U.S. patent application number 16/223075 was filed with the patent office on 2019-12-19 for methods of forming a bipolar transistor having a collector with a doping spike.
The applicant listed for this patent is SKYWORKS SOLUTIONS, INC.. Invention is credited to Kai Hay KWOK, Peter J. ZAMPARDI, JR..
Application Number | 20190386123 16/223075 |
Document ID | / |
Family ID | 49476529 |
Filed Date | 2019-12-19 |
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United States Patent
Application |
20190386123 |
Kind Code |
A1 |
ZAMPARDI, JR.; Peter J. ; et
al. |
December 19, 2019 |
METHODS OF FORMING A BIPOLAR TRANSISTOR HAVING A COLLECTOR WITH A
DOPING SPIKE
Abstract
This disclosure relates to methods of forming bipolar
transistors, such as heterojunction bipolar transistors. The
methods may include forming a sub-collector over a substrate,
forming a first portion of a collector over the sub-collector and
doping a second portion of the collector to form a doping spike.
The method may further include forming a third portion of the
collector over the doping spike and forming a base of the bipolar
transistor over the third portion of the collector.
Inventors: |
ZAMPARDI, JR.; Peter J.;
(Newbury Park, CA) ; KWOK; Kai Hay; (Thousand
Oaks, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SKYWORKS SOLUTIONS, INC. |
Woburn |
MA |
US |
|
|
Family ID: |
49476529 |
Appl. No.: |
16/223075 |
Filed: |
December 17, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15666465 |
Aug 1, 2017 |
10158010 |
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16223075 |
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15197611 |
Jun 29, 2016 |
9722058 |
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15666465 |
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14720519 |
May 22, 2015 |
9385200 |
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15197611 |
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13870682 |
Apr 25, 2013 |
9070732 |
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14720519 |
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61639784 |
Apr 27, 2012 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 29/0821 20130101;
H01L 29/0826 20130101; H01L 2223/6683 20130101; H01L 29/73
20130101; H01L 29/165 20130101; H01L 29/205 20130101; H01L 2223/665
20130101; H01L 29/7325 20130101; H01L 29/737 20130101; H01L 23/66
20130101; H01L 29/365 20130101; H01L 29/66242 20130101; H03F 3/195
20130101; H01L 2223/6677 20130101; H01L 29/36 20130101; H01L
2223/6655 20130101; H01L 29/7371 20130101; H03F 3/213 20130101;
H03F 2200/451 20130101; H01L 29/7378 20130101 |
International
Class: |
H01L 29/737 20060101
H01L029/737; H01L 29/73 20060101 H01L029/73; H01L 29/36 20060101
H01L029/36; H01L 29/08 20060101 H01L029/08; H01L 29/732 20060101
H01L029/732; H01L 23/66 20060101 H01L023/66; H01L 29/165 20060101
H01L029/165; H01L 29/205 20060101 H01L029/205; H01L 29/66 20060101
H01L029/66 |
Claims
1. A method of forming a bipolar transistor comprising: forming a
sub-collector over a substrate; forming a first portion of a
collector over the sub-collector; doping a second portion of the
collector to form a doping spike; forming a third portion of the
collector over the doping spike; and forming a base of the bipolar
transistor over the third portion of the collector.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 15/666,465, filed Aug. 1, 2017, titled
"METHODS OF FORMING A BIPOLAR TRANSISTOR HAVING A COLLECTOR WITH A
DOPING SPIKE," which is a continuation of U.S. patent application
Ser. No. 15/197,611, filed Jun. 29, 2016, titled "BIPOLAR
TRANSISTOR HAVING COLLECTOR WITH DOPING SPIKE," which is a
continuation of Ser. No. 14/720,519, filed May 22, 2015, titled
"BIPOLAR TRANSISTOR HAVING COLLECTOR WITH DOPING SPIKE," which is a
continuation of U.S. patent application Ser. No. 13/870,682, filed
Apr. 25, 2013, titled "BIPOLAR TRANSISTOR HAVING COLLECTOR WITH
DOPING SPIKE," which claims the benefit of priority under 35 U.S.C.
.sctn. 119(e) of U.S. Provisional Patent Application No.
61/639,784, filed Apr. 27, 2012, titled "BIPOLAR TRANSISTOR HAVING
COLLECTOR WITH DOPING SPIKE," the disclosures of each of which are
herein incorporated by reference in their entireties.
BACKGROUND
Technical Field
[0002] The present disclosure relates to the field of semiconductor
structures and, more particularly, to bipolar transistors and
products that include bipolar transistors.
Description of the Related Technology
[0003] Bipolar transistors, such as heterojunction bipolar
transistors (HBTs), are implemented in a wide variety of
applications. Such bipolar transistors can be formed on
semiconductor substrates, such as gallium arsenide (GaAs)
substrates. One illustrative application for a bipolar transistor
is in a power amplifier system. Specifications for power amplifier
systems have become more demanding to meet.
[0004] One aspect of transistor performance is linearity. Linearity
can also be a measure of performance of a power amplifier system.
Measures of linearity performance can include channel power ratios,
such as an adjacent channel power ratio (ACPR1) and an alternative
channel power ratio (ACPR2), and/or channel leakage power ratios,
such as an adjacent channel leakage power ratio (ACLR1) and an
alternative channel leakage power ratio (ACLR2). ACPR2 and ACLR2
can be referred to as second channel linearity measures. ACPR2 and
ACLR2 values can correspond at measurements at an offset of about
1.98 MHz from a frequency of interest.
[0005] Another aspect of transistor and/or power amplifier system
performance is safe operating area (SOA). SOA can be determined
from a breakdown voltage of a transistor, such as BV.sub.CEO.
BV.sub.CEO can represent a breakdown voltage from collector to
emitter with an open circuit at the base. BV.sub.CEO can be a
direct current (DC) measurement.
[0006] A need exists for transistors with improved linearity and/or
SOA in a variety of systems, such as power amplifier systems.
SUMMARY OF CERTAIN INVENTIVE ASPECTS
[0007] The innovations described in the claims each have several
aspects, no single one of which is solely responsible for its
desirable attributes. Without limiting the scope of the claims,
some prominent features will now be briefly described.
[0008] One aspect of this disclosure is a bipolar transistor that
includes a collector, a base disposed over the collector, and an
emitter. The collector has a collector width between a first end
and a second end opposite the first end. The base abuts the first
end of the collector at a base-collector junction. The collector
has a doping spike disposed closer to the base-collector junction
than to the second end of the collector.
[0009] In certain embodiments, the doping spike is at a
homojunction of the bipolar transistor. According to some
embodiments, the doping spike is disposed at a location that
results in approximately a local maximum of BV.sub.CEO of the
bipolar transistor. The doping spike is configured to improve
second channel linearity of the bipolar transistor without
substantially degrading BV.sub.CEO of the bipolar transistor,
according to a number of embodiments.
[0010] The doping spike is disposed within about 1/3 of the
collector width from the base-collector junction in a number of
embodiments. The doping spike is disposed within about 3/10 of the
collector width from the base-collector junction according to
various embodiments. In some embodiments, the doping spike is
disposed within about 1/4 of the collector width from the
base-collector junction. The doping spike is disposed within about
1/8 of the collector width from the base-collector junction
according to certain embodiments. The doping spike is disposed
within about 1/10 of the collector width from the base-collector
junction in some embodiments.
[0011] The doping spike is disposed within about 0.5 .mu.m from the
base-collector junction in certain embodiment. According to some
embodiments, the doping spike is disposed within about 0.3 .mu.m
from the base-collector junction. In various embodiments, the
doping spike is disposed within about 0.2 .mu.m from the
base-collector junction. The doping spike is disposed within about
0.15 .mu.m from the base-collector junction in a number of
embodiments. According to certain embodiments, the doping spike is
disposed within about 0.1 .mu.m from the base-collector
junction.
[0012] In accordance with certain embodiments, the doping spike has
a doping concentration of at least about 2.times.10.sup.17
cm.sup.-3. The doping spike has a doping concentration of at least
about 1.times.10.sup.18 cm.sup.-3 in some embodiments.
[0013] The doping spike has thickness of no more than about 200
.ANG. according to a number of embodiments.
[0014] The base has a substantially flat doping in certain
embodiments.
[0015] According to various embodiments, the collector further
includes a grading that begins at a point farther from the
base-collector junction than the doping spike.
[0016] The collector has a substantially flat doping besides the
doping spike according to certain embodiments. In some of these
embodiments, the substantially flat doping has a doping
concentration that is at least one order of magnitude less than the
doping concentration of the doping spike. In accordance with
various embodiments, the substantially flat doping has a doping
concentration that is at least two orders of magnitude less than
the doping concentration of the doping spike. The substantially
flat doping has a doping concentration selected from the range from
about 7.times.10.sup.15 cm.sup.-3 to 3.times.10.sup.16 cm.sup.-3
according to a number of embodiments.
[0017] The bipolar transistor also includes a sub-collector
abutting the second end of the collector according to some
embodiments.
[0018] The doping spike is configured to improve ACPR2 without
substantially degrading a breakdown voltage of the bipolar
transistor in certain embodiments.
[0019] In some embodiments, a thickness of the collector region is
selected from a range of about 3000 .ANG. to 11000 .ANG..
[0020] The bipolar transistor is a single heterojunction bipolar
transistor (HBT) according to certain embodiments.
[0021] According to certain embodiments, the bipolar transistor is
a GaAs transistor. In some other embodiments, the bipolar
transistor is a SiGe transistor.
[0022] Another aspect of this disclosure is a power amplifier
module that includes a power amplifier. The power amplifier is
configured to receive a radio frequency (RF) signal and generate an
amplified RF signal from the received RF signal. The power
amplifier includes a bipolar transistor having a collector, a base
abutting the collector at a base-collector junction, and an
emitter. The collector has a collector thickness from the
base-collector junction to an opposing end of the collector. The
collector includes a doping spike located within half of the
collector thickness from the base-collector junction.
[0023] In certain embodiments, the doping spike is at a
homojunction of the bipolar transistor.
[0024] According to some embodiments, the collector includes a
grading farther from the base-collector junction than the doping
spike.
[0025] The doping spike is located within about 1/4 of the
collector thickness from the base-collector junction in a number of
embodiments. The doping spike is located within about 1/10 of the
collector thickness from the base-collector junction according to
some embodiments. The doping spike is located within about 0.2
.mu.m from the base-collector junction in accordance with various
embodiments. The doping spike is located within about 0.5 .mu.m
from the base-collector junction in certain embodiments.
[0026] According to some embodiments, the doping spike has a doping
concentration on the order of at least about 1.times.10.sup.17
cm.sup.-3.
[0027] The doping spike has thickness of no more than about 150
.ANG. in various embodiments.
[0028] The bipolar transistor is a single heterojunction bipolar
transistor according to a number of embodiments.
[0029] According to certain embodiments, the doping spike is
configured to improve second channel linearity.
[0030] Another aspect of this disclosure is a power amplifier die
that includes a bipolar transistor. The bipolar transistor has a
collector, a base abutting the collector, and an emitter. The
collector has a doping spike at a homojunction within about 0.5
.mu.m of an interface between the base and the collector.
[0031] Another aspect of this disclosure is a mobile device that
includes an antenna, a battery, and a power amplifier. The power
amplifier includes a heterojunction bipolar transistor having a
collector with a collector thickness, a base, and an emitter. The
collector includes a first collector region abutting the base and
having a doping spike within about 1/3 of the collector thickness
from an interface of the base and the collector. The doping spike
is configured to improve second channel linearity of the power
amplifier.
[0032] Yet another aspect of this disclosure is a method of forming
a bipolar transistor. The method includes depositing a portion of a
collector of the bipolar transistor on a sub-collector of the
bipolar transistor, doping another portion of the collector to form
a doping spike in the collector, and forming a base of the bipolar
transistor such that the doping spike in the collector is within
about half of a collector thickness of the interface between the
collector and the base.
[0033] For purposes of summarizing the disclosure, certain aspects,
advantages and novel features of the inventions have been described
herein. It is to be understood that not necessarily all such
advantages may be achieved in accordance with any particular
embodiment of the invention. Thus, the inventions may be embodied
or carried out in a manner that achieves or optimizes one advantage
or group of advantages as taught herein without necessarily
achieving other advantages as may be taught or suggested
herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0034] FIG. 1A depicts an illustrative cross section of a bipolar
transistor according to an embodiment.
[0035] FIG. 1B is a graph of example doping concentrations of
portions of the bipolar transistor of FIG. 1A.
[0036] FIG. 1C is a legend illustrating example materials
corresponding to portions of the bipolar transistor of FIG. 1A.
[0037] FIG. 2A is a graph that illustrates relationships between
current density and collector-emitter voltage for various spike
locations in GaAs transistors.
[0038] FIG. 2B is a graph that illustrates relationships between
current density and collector-emitter voltage for various spike
doping concentrations in GaAs transistors.
[0039] FIGS. 2C-2F are graphs that illustrate relationships between
cut-off frequency and current density for various spike locations
in SiGe transistors and relationships between current density and
collector-emitter voltage for various spike doping concentrations
in SiGe transistors.
[0040] FIG. 3A depicts an illustrative cross section of a bipolar
transistor according to another embodiment.
[0041] FIG. 3B is a graph of example doping concentrations of
portions of the bipolar transistor of FIG. 3A.
[0042] FIG. 3C is a legend illustrating example materials
corresponding to portions of the bipolar transistor of FIG. 3A.
[0043] FIG. 4 is an illustrative flow diagram of making a bipolar
transistor according to an embodiment.
[0044] FIG. 5 is an illustrative block diagram of a power amplifier
module that includes a bipolar transistor with one or more features
described herein.
[0045] FIG. 6 is an illustrative block diagram of a mobile device
that includes the power amplifier module of FIG. 5.
DETAILED DESCRIPTION OF SOME EMBODIMENTS
[0046] Generally described, aspects of the present disclosure
relate to a bipolar transistor having a doping spike in the
collector relatively close to the base-collector junction. The
doping spike in the collector can be disposed so as to improve
linearity, such as second channel linearity, while substantially
maintaining the breakdown voltage BV.sub.CEO of the bipolar
transistor. The doping spike can be disposed at a location that
results in approximately a local maximum breakdown voltage
BV.sub.CEO of the bipolar transistor. The doping spike can be at a
homojunction of the bipolar transistor. Bipolar transistors with
one or more features of the doping spikes described herein can be
implemented in a power amplifier system.
[0047] Certain placements of a doping spike in the collector of a
bipolar transistor can decrease BV.sub.CEO while improving
ruggedness of the bipolar transistor. These placements of the
doping spike have not shown improvement in the linearity of the
bipolar transistor.
[0048] There have also been observed drawbacks to including a
doping spike in the collector of a bipolar transistor near the
base-collector junction. For instance, certain placements of the
doping spike in the collector near the base-collector junction can
degrade gain of the bipolar transistor. Alternatively or
additionally, a doping spike can create issues related to changes
in capacitance in the collector compared to including a different
doping profile in a wider area of the collector. Such capacitance
can degrade RF gain in certain circumstances.
[0049] Experimental data indicate that placing a doping spike in
the collector near the base-collector junction can improve second
channel linearity, such as ACPR2. In particular, single
heterojunction bipolar transistors (single HBTs) have shown
improvement in ACPR2 as a result of including a doping spike in the
collector near a base-collector interface.
[0050] Additionally, previous data on doping spikes, for example,
from lo-hi-lo IMPATT diodes, show a monotonic decrease in break
down voltage as the doping spike in the collector is moved closer
to the base-collector junction. However, as described herein, the
inventors have appreciated that placement of the doping spike
relative to the base-collector junction can result in the break
down voltage varying non-monotonically. In particular, the
inventors have appreciated that break down voltage can reach a
maximum and then decrease at certain placements of the doping spike
in the collector near the base-collector junction.
[0051] Including a doping spike at a homojunction of the collector
in such placements can improve linearity, such as second channel
linearity, without substantially reducing breakdown voltage, such
as BV.sub.CEO. As one example, including a doping spike within
about 1000 .ANG. of a base-collector junction in a collector having
a total collector thickness of about 1.1 .mu.m shows improved ACPR2
while maintaining BV.sub.CEO. In this example, the doping spike has
shown improved alternating current (AC) performance.
[0052] Experimental data indicate that a doping spike in a
collector can cause a relatively large drop of an electric field at
the location of the spike. After the peak electric field exceeds a
threshold level for impact ionization to occur, as the collector
current increases, the peak electric field (and thus the breakdown
region) appears to shift toward a sub-collector on an opposite side
of the collector than the base. This can be inferred, for example,
from an electric field profile and impact ionization rate plots.
Compared to other collector doping profiles (for example, a step
doped collector), the collector with a doping spike also appears to
allow the electric field to punch through. Data indicate that the
doping spike can provide an "extra" region between the doping spike
and the sub-collector for a depletion layer to expand or for the
electric field to build up, or the V.sub.CB to increase before snap
back occurs. This can result in a larger BV.sub.CEX for a collector
that includes a doping spike. However, this "extra" region can get
smaller as the doping spike is placed closer to the sub-collector.
As a result, the BV.sub.CEX of a transistor that includes the
doping spike near the sub-collector may not improve.
[0053] FIG. 1A shows an illustrative cross section of a bipolar
transistor 100 according to an embodiment. As illustrated, the
bipolar transistor 100 is a heterojunction bipolar transistor
(HBT). The bipolar transistor 100 can be formed on a substrate 106.
The substrate 106 can be a semiconductor substrate, such as a GaAs
substrate or a Si substrate. The bipolar transistor 100 can be
disposed between isolation regions 110 and 112. Isolation regions
110 and 112 are non-conductive regions that can provide electrical
isolation between the bipolar transistor 100 and an adjacent
transistor or other circuit element. Isolation regions 110 and 112
can each include, for example, a trench filled with nitride,
polyimide, or other material suitable for electrical isolation.
[0054] The bipolar transistor 100 can include a collector 120, a
base 121, and an emitter 124. A first end of the collector 120 can
abut the base 121. This can form a base-collector junction. The
base-collector junction can be a p-n junction. The collector 120
can include, for example, N- doped GaAs at the interface with the
base 121. A second end of the collector 120 that is opposite the
first end can abut the sub-collector 108. A thickness of the
collector 120 can represent the distance from the first end of the
collector to the second end of the collector. The collector
thickness can also equivalently be referred to as the collector
width. In the bipolar transistor 100 illustrated in FIG. 1A, the
collector thickness can be the distance from the interface between
the collector 120 and the base 121 and the interface between the
collector 120 and the sub-collector 108. In certain embodiments,
the thickness of the collector 120 can be selected from the range
of about 0.3 .mu.m to 1.1 .mu.m, such as from or about 0.5 .mu.m to
1.1 .mu.m.
[0055] The collector 120 can include a doping spike 125. The
collector 120 can also include a flat doped portion 150 outside of
the doping spike 125. As illustrated in FIG. 1A, the flat doped
portion 150 of the collector region 120 can include all or
substantially all of the collector 120 outside of the doping spike
125. The flat doped portion 150 can include N- doped GaAs and the
doping spike can include N+ doped GaAs. Alternatively, in some
other embodiments (not shown), flat doped portion 150 can include
P- doped GaAs and the doping spike can include P+ doped GaAs. The
flat doped portion 150 can have a substantially flat doping. The
doping concentration in the flat doped portion 150 can be at least
about one, two, or three orders of magnitude less than the doping
concentration in the doping spike 125. In some embodiments, the
flat doped portion 150 can have a doping concentration selected in
the range from about 7.times.10.sup.15 cm.sup.-3 to
1.times.10.sup.16 cm.sup.-3.
[0056] The doping spike 125 is relatively thin. In the bipolar
transistor 100 illustrated in FIG. 1A, the thickness of the doping
spike 125 can be measured in a direction substantially parallel to
the base-collector junction. In certain embodiments, the doping
spike 125 can have a non-zero thickness of less than or equal to
about 200 .ANG., 150 .ANG., 100 .ANG., or 50 .ANG.. For instance,
the doping spike 125 can have a thickness of about 100 .ANG..
[0057] The doping spike 125 can be disposed so as to improve second
channel linearity of the bipolar transistor 100 and to not degrade
BV.sub.CEO. For instance, the doping spike 125 can be disposed at
or near a location that results in a local maximum of BV.sub.CEO of
the transistor 100. The placement of the doping spike 125 can
improve BV.sub.CEX while improving second channel linearity and
without substantially degrading BV.sub.CEO. The doping spike can be
disposed to improve large signal linearity of the bipolar
transistor 100. As illustrated in FIG. 1A, the doping spike 125 is
relatively close to the base-collector junction. The doping spike
125 can be closer to the first end of the 120 at the base-collector
junction than the second end of the collector 120 that is opposite
the first end of the collector (for example, the interface with the
sub-collector 108 in the embodiment illustrated in FIG. 1A). In
certain embodiments, the doping spike 125 is disposed within about
1/2 of the collector width from the base-collector junction, within
about of the collector width from the base-collector junction,
within about 1/3 of the collector width from the base-collector
junction, within about 3/10 of the collector width from the
base-collector junction, within about 3/11 of the collector width
from the base-collector junction, within about 1/4 of the collector
width from the base-collector junction, within about 1/5 of the
collector width from the base-collector junction, within about 1/6
of the collector width from the base-collector junction, within
about 1/8 of the collector width from the base-collector junction,
or within about 1/10 of the collector width from the base-collector
junction. In some embodiments, the doping spike 125 can be disposed
within about 0.5 .mu.m from the base-collector junction, within
about 0.45 .mu.m from the base-collector junction, within about 0.4
.mu.m from the base-collector junction, within about 0.35 .mu.m
from the base-collector junction, within about 0.3 .mu.m from the
base-collector junction, within about 0.25 .mu.m from the
base-collector junction, within about 0.2 .mu.m from the
base-collector junction, within about 0.15 .mu.m from the
base-collector junction, within about 0.12 .mu.m from the
base-collector junction, within about 0.1 .mu.m from the
base-collector junction, or within about 0.05 .mu.m from the
base-collector junction. As one example, the doping spike 125 can
be disposed about 0.1 .mu.m (1000 .ANG.) from the base-collector
junction of the bipolar transistor 100. As another example, the
doping spike 125 can be disposed about 0.3 .mu.m (3000 .ANG.) from
the base-collector junction of the bipolar transistor 100. One or
more of the doping spike placements described in this paragraph can
apply to any of the bipolar transistors described herein, such as
GaAs bipolar transistors or SiGe bipolar transistors.
[0058] The curves illustrated in FIG. 2A correspond to placements
of a doping spike at various distances from a base-collector
junction of the bipolar transistor 100 having a collector 120 with
a thickness of 1.1 .mu.m and a flat doping of approximately
7.5.times.10.sup.15 cm.sup.-3 outside of the doping spike 125.
[0059] The doping spike 125 can have a relatively high doping
concentration. For example, as indicated by the legend 180, the
doping spike 125 can be N+ doped. Since the doping spike 125 is N+
doped and the reminder of the collector 120 is N- doped, the doping
spike 125 is at a homojunction of the bipolar transistor 100
illustrated in FIG. 1A. In some other embodiments, the doping spike
125 can be P+ doped. According to some of these embodiments, the
remainder of the collector 120 can be P- doped.
[0060] In some embodiments, the doping concentration of the doping
spike 125 can be selected from the range from about
1.times.10.sup.17 cm.sup.-3 to 1.times.10.sup.19 cm.sup.-3.
According to certain embodiments, the doping concentration of the
doping spike 125 can be selected from one of the following ranges:
from about 2.times.10.sup.17 cm.sup.-3 to 1.times.10.sup.18
cm.sup.-3, from about 2.times.10.sup.17 cm.sup.-3 to
1.5.times.10.sup.18 cm.sup.-3, from about 2.times.10.sup.17
cm.sup.-3 to 2.times.10.sup.18 cm.sup.-3, from about
2.times.10.sup.17 cm.sup.-3 to 2.5.times.10.sup.18 cm.sup.-3 from
about 2.times.10.sup.17 cm.sup.-3 to 3.times.10.sup.18 cm.sup.-3,
from about 2.times.10.sup.17 cm.sup.-3 to 5.times.10.sup.18
cm.sup.-3, or from about 2.times.10.sup.17 cm.sup.-3 to
6.times.10.sup.18 cm.sup.-3. In accordance with some embodiments,
the doping concentration of the doping spike 125 can be at least
about 1.times.10.sup.17 cm.sup.-3, 2.times.10.sup.17 cm.sup.-3,
5.times.10.sup.17 cm.sup.-3, 7.times.10.sup.17 cm.sup.-3,
1.times.10.sup.18 cm.sup.-3, 1.5.times.10.sup.18 cm.sup.-3,
2.times.10.sup.18 cm.sup.-3, 2.5.times.10.sup.18 cm.sup.-3,
3.times.10.sup.18 cm.sup.-3, 4.times.10.sup.18 cm.sup.-3,
5.times.10.sup.18 cm.sup.-3, 7.times.10.sup.18 cm.sup.-3, or
1.times.10.sup.19 cm.sup.-3. As one example, the doping
concentration of the doping spike 125 can be approximately
2.times.10.sup.18 cm.sup.-3. One or more of the spike doping
concentrations described in this paragraph can apply to any of the
bipolar transistors described herein, such as GaAs bipolar
transistors or SiGe bipolar transistors.
[0061] FIG. 2B is a graph that illustrates relationships between
current density and collector-emitter voltage for various
concentrations of a doping spike of a bipolar transistor. The
curves illustrated in FIG. 2B correspond to different doping
concentrations of a doping spike 125 spaced 3000 .ANG. from a
base-collector junction of the bipolar transistor 100 having a
collector 120 with a thickness of 1.1 .mu.m and a flat doping of
approximately 7.5.times.10.sup.15 cm.sup.-3 outside of the doping
spike 125. The current-voltage curves illustrated in FIG. 2B appear
to start shifting to the right for doping spikes with a
concentration below about 2.times.10.sup.18 cm.sup.-3. When the
curves shift right, this can result in a higher BV.sub.CEO and
higher BV.sub.CEX but lower collector current for BV.sub.CEX. This
appears to show that as the doping concentration of the doping
spike is decreased, it becomes easier for the electric field to
punch through the doping spike. For instance, lower doping
concentrations should be closer to a uniform doped collector with a
higher BV.sub.CEO.
[0062] Referring back to FIG. 1A, the base 121 of the bipolar
transistor 100 can include P doped GaAs (for example, P+ doped
GaAs). The base 121 can have a substantially flat doping. The
bipolar transistor 100 can include a collector contact 136 to the
collector 120, base contact(s) 138 to the base 121, and an emitter
contact 142 to the emitter 126. These contacts can provide an
electrical connection to and/or from the bipolar transistor 100.
The contacts 136, 138, and 142 can be formed of any suitable
conductive material. As illustrated in FIG. 1A, the emitter contact
142 can be disposed over a top contact 134, a bottom contact 132,
and an emitter cap 126.
[0063] The bipolar transistor 100 can include a sub-collector 108
over the substrate 106. The sub-collector 108 can be under the
collector 120. As illustrated in FIG. 1A, the sub-collector 108 can
be disposed between the collector 120 and the substrate 106. The
sub-collector 108 can abut the second end of the collector 120. The
sub-collector 108 can be a flat doped region. The sub-collector 108
can have a doping concentration on the order of 1.times.10.sup.18
cm.sup.-3, such as about 5.times.10.sup.18 cm.sup.-3. The
sub-collector 108 can have a thickness of about 8000 .ANG. in
certain embodiments. The collector contact 136 can physically
contact the sub-collector 108 to provide an electrical connection
to the collector 120.
[0064] FIG. 1C is a legend 180 illustrating example materials
corresponding to portions of the bipolar transistor 100 of FIG. 1A.
Dashed lines between FIG. 1A and FIG. 1C are included to indicate
that materials in the legend 180 correspond to particular portions
of the bipolar transistor 100. The legend 180 indicates that, in
certain embodiments, the substrate 106 can be semi-insulating GaAs,
the sub-collector 108 can be N+ GaAs, the flat doped portion 150 of
the collector 150 can be N- GaAs, the doping spike 125 can be N+
GaAs, the base 121 can be P+ GaAs, the emitter 124 can be N- InGaP,
the emitter cap 126 can be N- GaAs, the bottom contact 132 can be
N+ GaAs, and the top contact 134 can be InGaAs.
[0065] It will be understood that in some embodiments, one or more
of the regions of the bipolar transistor 100 can include a suitable
alternative material instead of the example materials provided in
the legend 180. For example, in certain embodiments, the substrate
106 can be SiGe and one or more other regions of the bipolar
transistor 100 can also include Si and/or SiGe. If a doping spike
125 is implemented in a SiGe bipolar transistor, then the gain of
such transistors should improve as a result of including the doping
spike 125 relatively near the base-collector junction, for example,
as described with reference to FIG. 1A. This should result
improvement in RF gain of a power amplifier that includes such a
SiGe bipolar transistor.
[0066] Moreover, in any of the bipolar transistors described herein
n-type doping and p-type doping can be interchanged throughout some
or all of the transistor. Thus, any combination of features
described herein can be applied to NPN transistors and/or PNP
transistors.
[0067] FIGS. 2C-2F are graphs that illustrate relationships between
cut-off frequency and current density for various spike locations
in SiGe transistors and relationships between current density and
collector-emitter voltage for various spike doping concentrations
in SiGe transistors. The data in FIGS. 2C-2F corresponds to a SiGe
embodiment of the transistor 100 of FIG. 1A with the doping profile
shown in FIG. 1B. The graphs in FIGS. 2C-2D correspond to SiGe
transistors with a collector width of 1.1 .mu.m collector width, in
which the collector has a doping spike with a doping concentration
of 1.times.10.sup.18 cm.sup.-3 with the reminder of the collector
having a flat doping concentration of 7.5.times.10.sup.15
cm.sup.-3. The graphs in FIGS. 2E-2F correspond to SiGe transistors
with a collector width of 0.5 .mu.m, in which the collector has a
doping spike with a doping concentration of 1.times.10.sup.18
cm.sup.-3 with the reminder of the collector having a flat doping
concentration of 7.5.times.10.sup.15 cm.sup.-3. The data in FIGS.
2C and 2E corresponds to a voltage between the collector and the
emitter of 1 V. The SiGe transistors corresponding to the data in
FIGS. 2C-2F can have improved large signal linearity.
[0068] Simulation data indicate that, in general, the closer a
doping spike is disposed to the base of a SiGe bipolar transistor,
the lower the BV.sub.CEO. But when the spike is positioned too
close to the base, the breakdown curve can shift toward a higher
V.sub.CE region. The doping spike location where this occurs can
depend on the doping concentration of the doping spike. Based on
simulation data, this may occur for a doping spike with a doping
concentration of 1.times.10.sup.18 cm.sup.-3 in a SiGe bipolar
transistor and may not occur for a doping spike with doping spike
with a doping concentration of 2.times.10.sup.18 cm.sup.-3 in a
SiGe bipolar transistor. This may result from the magnitude of the
electric field peaking at base-collector junction and decreasing
towards the collector-sub-collector interface. Therefore, the
closer the spike is to base-collector junction and/or the lower the
spike doping is, the easier the spike can punch through (i.e., the
doping spike can become "transparent" to the breakdown).
[0069] As shown in FIG. 2C, peak cut-off frequency ft can increase
the position of the doping spike is moved from 8000 .ANG. away from
the base to 3000 .ANG. away from the base in a collector with a
width of 11000 .ANG.. Moving the doping spike closer to the base
can be like shortening the collector. This can reduce collector
transit time. But moving the doping spike closer than 3000 .ANG.
from the base-collector junction can start reducing the peak
cut-off frequency ft as the doping spike get punched through
(BV.sub.CEO starts increasing). Also, capacitance from the base to
the collector C.sub.BC can increase as the doping spike is placed
closer to the base. Low current density cut-off frequency ft can
degrade. Overall, the doping spike appears to have higher current
density at peak cut-off frequency ft than the baseline. The doping
spike can be more effective at delaying the Kirk effect.
[0070] Simulation data indicate that the lower the spike doping,
the larger the BV.sub.CEO is as the doping spike is moved close to
the base (for example, 700 .ANG.from the base or 500 .ANG. from the
base).
[0071] As shown in FIG. 2E, peak cut-off frequency ft can increase
as the doping spike is moved from 3000 .ANG. away from the base to
2000 .ANG. away from the base in a collector with a width of 5000
.ANG.. Moving the doping spike closer to the base can be like
shortening the collector. This can reduce collector transit time.
But moving the doping spike closer than 2000 .ANG. from the base
can start reducing the peak cut-off frequency ft as the doping
spike get punched through (BV.sub.CEO starts increasing). Also,
capacitance from the base to the collector C.sub.BC can increase as
the doping spike is placed closer to the base. Low current density
cut-off frequency ft can degrade. Overall, the doping spike appears
to have higher current density at peak cut-off frequency ft than
the baseline. The doping spike can be more effective at delaying
the Kirk effect.
[0072] FIG. 3A depicts an illustrative cross section of a bipolar
transistor 300 according to another embodiment. The bipolar
transistor 300 of FIG. 3A is substantially the same as the bipolar
transistor 100 of FIG. 1A except the doping in the collector 320 of
FIG. 3A is different from the doping of the collector 120 of FIG.
1A. More specifically, the collector 320 includes a grading. FIG.
3B is a graph that shows illustrative doping concentrations of
portions of the bipolar transistor 300 of FIG. 3A.
[0073] The bipolar transistor 300 can include a collector 320
having a doping spike 125, a flat doped portion 150, and a graded
portion 330. The doping spike 125 and the flat doped portion 150
can include any combination of features described with reference to
the doping spike 125 and the flat doped portion 150 described with
references to FIGS. 1A-1C.
[0074] The graded portion 330 of the collector 320 includes a
grading in which doping concentration varies (for example,
increases) away from the base 121. Doping concentration can vary
linearly or non-linearly (for example, parabolically) in the
grading. For example, FIG. 3B illustrates a linear grade in doping
concentration in the graded portion 330. The grading in the graded
portion 330 can be farther from the base 121 than the doping spike
125. For example, as illustrated in FIG. 3A, the grading in the
graded portion 330 can be disposed between the doping spike 125 and
the sub-collector 108. The doping concentration in the grading in
the graded portion 330 can increase away from doping spike 125. In
one embodiment, the doping concentration can grade from about
3.times.10.sup.16 cm.sup.-3 to about 6.times.10.sup.16 cm.sup.-3 at
an interface with the sub-collector 108. According to some other
embodiments (not shown), the graded portion 300 can include two or
more gradings in which doping concentration varies (for example,
increases away from the base 121) at different rates.
[0075] The grading in the graded portion 330 can extend to an
interface with the sub-collector 108 according to certain
embodiments. In some of these embodiments, the maximum doping
concentration of the graded portion 330 can be about two orders of
magnitude lower than the doping concentration of the sub-collector
108. For example, the maximum doping concentration of the graded
portion 330 can be about 6.times.10.sup.16 cm.sup.-3 and the doping
concentration of the sub-collector 108 can be about
5.times.10.sup.18 cm.sup.-3.
[0076] The doping concentration of the collector 120 at an
interface with the sub-collector 108 can determine a breakdown
voltage from collector to emitter with the base to a potential via
a resistor. Such a breakdown voltage can be referred to as
"BV.sub.CEX." A higher BV.sub.CEX can increase a safe operating
area (SOA) and/or ruggedness of a bipolar transistor. Higher doping
in the graded portion 330 at the interface with the sub-collector
108 can reduce the SOA. Doping the graded portion 330 at the
interface with the sub-collector 108 too low can result in a
breakdown current that is too steep, thereby reducing robustness of
the bipolar transistor 300. In certain embodiments, the doping
concentration in the graded portion 330 at the interface with the
sub-collector 108 can be selected in the range from about
5.times.10.sup.16 cm.sup.-36 to 9.times.10.sup.16 cm.sup.-3. Such
doping concentrations can result in desirable BV.sub.CEX values for
the bipolar transistor 300 and/or a desirable SOA.
[0077] According to other embodiments (not shown), the collector
can include a relatively high doping at an interface with the base.
The relatively high doping can be at least about 3.times.10.sup.16
cm.sup.-3. For instance, the relatively high doping can be selected
from the range of about 3.times.10.sup.16 cm.sup.-3 to
9.times.10.sup.16 cm.sup.-3. Having a relatively high doping in the
collector at an interface with the base can improve linearity, such
as second channel linearity.
[0078] FIG. 4 is an illustrative flow diagram of a process 400 of
forming a bipolar transistor according to an embodiment. The
process 400 can be performed while forming the bipolar transistor
100 of FIG. 1A and/or the bipolar transistor 300 of FIG. 3A. As
such, the process 400 can form a variety of different types of
bipolar transistors, such as GaAs bipolar transistors and/or SiGe
bipolar transistors. At block 402, a sub-collector is formed over a
substrate. The sub-collector can include any combination of the
sub-collectors described herein, for example, the sub-collector
108. A portion of the collector can be formed (for example,
deposited) block 404. At block 406, another portion of the
collector can be doped to form a doping spike. The doping spike can
include one or more features of the doping spikes described herein.
After forming the doping spike, additional collector can be formed
over the doping spike. When the collector is fully formed, the
collector has a collector thickness, which can be any of the
collector thicknesses described herein. It will be understood that
the collector thickness does not include the thickness of the
sub-collector. The base of a bipolar transistor is formed at block
408. The base can include any combination of features of the bases
described herein, for example, the base 121. For instance, the base
can abut the collector. The base can be formed such that the doping
spike in the collector is near the interface of the base and the
collector.
[0079] In a bipolar transistor formed by the process 400, the
doping spike can be spaced from the base by any of the ratios
and/or distances described herein. For instance, the doping spike
can be formed within about half of the collector thickness of the
interface between the collector and the base. The doping spike can
be formed at a location of the collector that results in
substantially a maximum breakdown voltage of the bipolar
transistor. The doping spike can be formed at a position in the
collector near the collector-base interface such that linearity,
such as APCR2, is improved without substantially decreasing break
down voltage, such as BV.sub.CEO. In some embodiments, the
collector can also be doped to form a grading in the collector that
is farther from the base than the doping spike. The spiked doping
in the collector can improve AC performance of the bipolar
transistor. Alternatively or additionally, the spiked doping can
improve RF performance of the bipolar transistor.
[0080] It will be understood that any of the processes discussed
herein, such as the process 400, may include greater or fewer
operations and the operations may be performed in any order, as
appropriate. For example, in some Si bipolar transistors 100 and/or
300, the base may be formed prior to forming the collector and the
doping spike can be formed after forming the base. Further, one or
more acts of the processes discussed herein, such as the process
400, can be performed either serially or in parallel.
[0081] FIG. 5 is a schematic block diagram of a module 520 that can
include one or more bipolar transistors 100 of FIG. 1A and/or one
or more bipolar transistors 300 of FIG. 3. The module 520 can be
some or all of a power amplifier system. The module 520 can be
referred to as multi-chip module and/or a power amplifier module in
some implementations. The module 520 can include a substrate 522
(for example, a packaging substrate), a die 524 (for example, a
power amplifier die), a matching network 525, the like, or any
combination thereof. Although not illustrated, the module 520 can
include one or more other dies and/or one or more circuit elements
that coupled to the substrate 522 in some implementations. The one
or more other dies can include, for example, a controller die,
which can include a power amplifier bias circuit and/or a direct
current-to-direct current (DC-DC) converter. Example circuit
element(s) mounted on the packaging substrate can include, for
example, inductor(s), capacitor(s), impedance matching network(s),
the like, or any combination thereof.
[0082] The module 520 can include a plurality of dies and/or other
components mounted on and/or coupled to the substrate 522 of the
module 520. In some implementations, the substrate 522 can be a
multi-layer substrate configured to support the dies and/or
components and to provide electrical connectivity to external
circuitry when the module 520 is mounted on a circuit board, such
as a phone board.
[0083] The power amplifier die 524 can receive a RF signal at an
input pin RF_IN of the module 520. The power amplifier die 524 can
include one or more power amplifiers, including, for example,
multi-stage power amplifiers configured to amplify the RF signal.
The power amplifier die 524 can include an input matching network
530, a first stage power amplifier 532 (which can be referred to as
a driver amplifier (DA)), an inter-stage matching network 534, a
second stage power amplifier 536 (which can be referred to as an
output amplifier (OA)), or any combination thereof.
[0084] A power amplifier can include the first stage power
amplifier 532 and the second stage power amplifier 536. The first
stage power amplifier 532 and/or the second stage power amplifier
536 can include one or more bipolar transistors 100 of FIG. 1A
and/or one or more bipolar transistors 300 of FIG. 3A. Moreover,
the bipolar transistor 100 of FIG. 1A and/or the bipolar transistor
300 of FIG. 3A can improve linearity, such as ACPR2, of the power
module 520 and/or the power amplifier die 524 without substantially
degrading break down voltage, such as BV.sub.CEO.
[0085] The RF input signal can be provided to the first stage power
amplifier 532 via the input matching network 530. The matching
network 530 can receive a first stage bias signal. The first bias
signal can be generated on the PA die 524, outside of the PA die
524 in the module 520, or external to the module 520. The first
stage power amplifier 532 can amplify the RF input and provide the
amplified RF input to the second stage power amplifier 536 via the
inter-stage matching circuit 534. The inter-stage matching circuit
534 can receive a second stage bias signal. The second stage bias
signal can be generated on the PA die 524, outside of the PA die
524 in the module 520, or external to the module 520. The second
stage power amplifier 536 can generate the amplified RF output
signal.
[0086] The amplified RF output signal can be provided to an output
pin RF_OUT of the power amplifier die 524 via an output matching
network 525. The matching network 525 can be provided on the module
520 to aid in reducing signal reflections and/or other signal
distortions. The power amplifier die 524 can be any suitable die.
In some implementations, the power amplifier 524 die is a gallium
arsenide (GaAs) die. In some of these implementations, the GaAs die
has transistors formed using a heterojunction bipolar transistor
(HBT) process. In some other implementations, the power amplifier
die is a silicon germanium (SiGe) die.
[0087] The module 520 can also include a one or more power supply
pins, which can be electrically connected to, for example, the
power amplifier die 524. The one or more power supply pins can
provide supply voltages to the power amplifiers, such as
V.sub.SUPPLY1 and V.sub.SUPPLY2, which can have different voltage
levels in some implementations. The module 520 can include circuit
element(s), such as inductor(s), which can be formed, for example,
by a trace on the multi-chip module. The inductor(s) can operate as
a choke inductor, and can be disposed between the supply voltage
and the power amplifier die 524. In some implementations, the
inductor(s) are surface mounted. Additionally, the circuit
element(s) can include capacitor(s) electrically connected in
parallel with the inductor(s) and configured to resonate at a
frequency near the frequency of a signal received on the pin RF_IN.
In some implementations, the capacitor(s) can include a surface
mounted capacitor.
[0088] The module 520 can be modified to include more or fewer
components, including, for example, additional power amplifier
dies, capacitors and/or inductors. For instance, the module 520 can
include one or more additional matching networks 525. As another
example, the module 520 can include an additional power amplifier
die, as well as an additional capacitor and inductor configured to
operate as a parallel LC circuit disposed between the additional
power amplifier die and the power supply pin of the module 520. The
module 520 can be configured to have additional pins, such as in
implementations in which a separate power supply is provided to an
input stage disposed on the power amplifier die 520 and/or
implementations in which the module 520 operates over a plurality
of bands.
[0089] The module 520 can have a low voltage positive bias supply
of about 3.2 V to 4.2 V, good linearity (for example, meeting any
of the second channel linearity specification described herein),
high efficiency (for example, PAE of approximately 40% at 28.25
dBm), large dynamic range, a small and low profile package (for
example, 3 mm.times.3 mm.times.0.9 mm with a 10-pad configuration),
power down control, support low collector voltage operation,
digital enable, not require a reference voltage, CMOS compatible
control signals, an integrated directional coupler, or any
combination thereof.
[0090] In some implementations, the module 520 is a power amplifier
module that is a fully matched 10-pad surface mount module
developed for Wideband Code Division Multiple Access (WCDMA)
applications. This small and efficient module can pack full
1920-1980 MHz bandwidth coverage into a single compact package.
Because of high efficiencies attained throughout the entire power
range, the module 520 can deliver desirable talk-time advantages
for mobile phones. The module 520 can meet the stringent spectral
linearity requirements of High Speed Downlink Packet Access
(HSDPA), High Speed Uplink Packet Access (HSUPA), and Long Term
Evolution (LTE) data transmission with high power added efficiency.
A directional coupler can be integrated into the module 520 and can
thus eliminate the need for an external coupler.
[0091] The die 524 can be a power amplifier die embodied in a
single Gallium Arsenide (GaAs) Microwave Monolithic Integrated
Circuit (MMIC) that includes all active circuitry of the module
520, such as one or more bipolar transistors 100 of FIG. 1A and/or
one or more bipolar transistors 300 of FIG. 3A. The MMIC can
include on-board bias circuitry, as well as input matching network
530 and inter-stage matching network 534. An output matching
network 525 can have a 50 ohm load that is embodied separate from
the die 524 within the package of the module 520 to increase and/or
optimize efficiency and power performance.
[0092] The module 520 can be manufactured with a GaAs
Heterojunction Bipolar Transistor (HBT) BiFET process that provides
for all positive voltage DC supply operation while maintaining high
efficiency and good linearity (for example, meeting any of the
second channel linearity specification described herein). Primary
bias to the module 520 can be supplied directly or via an
intermediate component from any three-cell Ni--Cd battery, a
single-cell Li-Ion battery, or other suitable battery with an
output in the range selected from about 3.2 to 4.2 V. No reference
voltage is needed in some implementations. Power down can be
accomplished by setting an enable voltage to zero volts. No
external supply side switch is needed as typical "off" leakage is a
few microamperes with full primary voltage supplied from the
battery, according to some implementations.
[0093] Any of the devices, systems, methods, and apparatus
described herein can be implemented in a variety of electronic
devices, such as a mobile device, which can also be referred to as
a wireless device. FIG. 6 is a schematic block diagram of an
example mobile device 601 that can include one or more bipolar
transistors 100 of FIG. 1A and/or one or more bipolar transistors
300 of FIG. 3A.
[0094] Examples of the mobile device 601 can include, but are not
limited to, a cellular phone (for example, a smart phone), a
laptop, a tablet computer, a personal digital assistant (PDA), an
electronic book reader, and a portable digital media player. For
instance, the mobile device 601 can be a multi-band and/or
multi-mode device such as a multi-band/multi-mode mobile phone
configured to communicate using, for example, Global System for
Mobile (GSM), code division multiple access (CDMA), 3G, 4G, and/or
long term evolution (LTE).
[0095] In certain embodiments, the mobile device 601 can include
one or more of a switching component 602, a transceiver component
603, an antenna 604, power amplifiers 605 that can include one or
more bipolar transistors 100 of FIG. 1A and/or one or more bipolar
transistors 300 of FIG. 3A, a control component 606, a computer
readable medium 607, a processor 608, a battery 609, and supply
control block 610.
[0096] The transceiver component 603 can generate RF signals for
transmission via the antenna 604. Furthermore, the transceiver
component 603 can receive incoming RF signals from the antenna
604.
[0097] It will be understood that various functionalities
associated with the transmission and receiving of RF signals can be
achieved by one or more components that are collectively
represented in FIG. 6 as the transceiver 603. For example, a single
component can be configured to provide both transmitting and
receiving functionalities. In another example, transmitting and
receiving functionalities can be provided by separate
components.
[0098] Similarly, it will be understood that various antenna
functionalities associated with the transmission and receiving of
RF signals can be achieved by one or more components that are
collectively represented in FIG. 6 as the antenna 604. For example,
a single antenna can be configured to provide both transmitting and
receiving functionalities. In another example, transmitting and
receiving functionalities can be provided by separate antennas. In
yet another example, different bands associated with the mobile
device 601 can be provided with different antennas.
[0099] In FIG. 6, one or more output signals from the transceiver
603 are depicted as being provided to the antenna 604 via one or
more transmission paths. In the example shown, different
transmission paths can represent output paths associated with
different bands and/or different power outputs. For instance, the
two example power amplifiers 605 shown can represent amplifications
associated with different power output configurations (e.g., low
power output and high power output), and/or amplifications
associated with different bands.
[0100] In FIG. 6, one or more detected signals from the antenna 604
are depicted as being provided to the transceiver 603 via one or
more receiving paths. In the example shown, different receiving
paths can represent paths associated with different bands. For
example, the four example paths shown can represent quad-band
capability that some mobile devices 601 are provided with.
[0101] To facilitate switching between receive and transmit paths,
the switching component 602 can be configured to electrically
connect the antenna 604 to a selected transmit or receive path.
Thus, the switching component 602 can provide a number of switching
functionalities associated with an operation of the mobile device
601. In certain embodiments, the switching component 602 can
include a number of switches configured to provide functionalities
associated with, for example, switching between different bands,
switching between different power modes, switching between
transmission and receiving modes, or some combination thereof. The
switching component 602 can also be configured to provide
additional functionality, including filtering of signals. For
example, the switching component 602 can include one or more
duplexers.
[0102] The mobile device 601 can include one or more power
amplifiers 605. RF power amplifiers can be used to boost the power
of a RF signal having a relatively low power. Thereafter, the
boosted RF signal can be used for a variety of purposes, including
driving the antenna of a transmitter. Power amplifiers 605 can be
included in electronic devices, such as mobile phones, to amplify a
RF signal for transmission. For example, in mobile phones having a
an architecture for communicating under the 3G and/or 4G
communications standards, a power amplifier can be used to amplify
a RF signal. It can be desirable to manage the amplification of the
RF signal, as a desired transmit power level can depend on how far
the user is away from a base station and/or the mobile environment.
Power amplifiers can also be employed to aid in regulating the
power level of the RF signal over time, so as to prevent signal
interference from transmission during an assigned receive time
slot. A power amplifier module can include one or more power
amplifiers.
[0103] FIG. 6 shows that in certain embodiments, a control
component 606 can be provided, and such a component can include
circuitry configured to provide various control functionalities
associated with operations of the switching component 602, the
power amplifiers 605, the supply control 610, and/or other
operating component(s).
[0104] In certain embodiments, a processor 608 can be configured to
facilitate implementation of various functionalities described
herein. Computer program instructions associated with the operation
of any of the components described herein may be stored in a
computer-readable memory 607 that can direct the processor 608,
such that the instructions stored in the computer-readable memory
produce an article of manufacture including instructions which
implement the various operating features of the mobile devices,
modules, etc. described herein.
[0105] The illustrated mobile device 601 also includes the supply
control block 610, which can be used to provide a power supply to
one or more power amplifiers 605. For example, the supply control
block 610 can include a DC-to-DC converter. However, in certain
embodiments the supply control block 610 can include other blocks,
such as, for example, an envelope tracker configured to vary the
supply voltage provided to the power amplifiers 605 based upon an
envelope of the RF signal to be amplified.
[0106] The supply control block 610 can be electrically connected
to the battery 609, and the supply control block 610 can be
configured to vary the voltage provided to the power amplifiers 605
based on an output voltage of a DC-DC converter. The battery 609
can be any suitable battery for use in the mobile device 601,
including, for example, a lithium-ion battery. With at least one
power amplifier 605 that includes one or more bipolar transistors
100 of FIG. 1A and/or one or more bipolar transistors 300 of FIG.
3A, the power consumption of the battery 609 can be reduced and/or
the reliability of the power amplifier 605 can be improved, thereby
improving performance of the mobile device 601.
[0107] Some of the embodiments described above have provided
examples in connection with modules and/or electronic devices that
include power amplifiers, such as mobile phones. However, the
principles and advantages of the embodiments can be used for any
other systems or apparatus that have needs for a bipolar transistor
with a high level of second channel linearity without degrading
break down voltage.
[0108] Systems implementing one or more aspects of the present
disclosure can be implemented in various electronic devices.
Examples of electronic devices can include, but are not limited to,
consumer electronic products, parts of the consumer electronic
products, electronic test equipment, etc. More specifically,
electronic devices configured implement one or more aspects of the
present disclosure can include, but are not limited to, an RF
transmitting device, any portable device having a power amplifier,
a mobile phone (for example, a smart phone), a telephone, a base
station, a femtocell, a radar, a device configured to communication
according to the WiFi and/or Bluetooth standards, a television, a
computer monitor, a computer, a hand-held computer, a tablet
computer, a laptop computer, a personal digital assistant (PDA), a
microwave, a refrigerator, an automobile, a stereo system, a DVD
player, a CD player, a VCR, an MP3 player, a radio, a camcorder, a
camera, a digital camera, a portable memory chip, a washer, a
dryer, a washer/dryer, a copier, a facsimile machine, a scanner, a
multi functional peripheral device, a wrist watch, a clock, etc.
Part of the consumer electronic products can include a multi-chip
module including an RF transmission line, a power amplifier module,
an integrated circuit including an RF transmission line, a
substrate including an RF transmission line, the like, or any
combination thereof. Moreover, other examples of the electronic
devices can also include, but are not limited to, memory chips,
memory modules, circuits of optical networks or other communication
networks, and disk driver circuits. Further, the electronic devices
can include unfinished products.
[0109] Unless the context clearly requires otherwise, throughout
the description and the claims, the words "comprise," "comprising,"
and the like are to be construed in an inclusive sense, as opposed
to an exclusive or exhaustive sense; that is to say, in the sense
of "including, but not limited to." The words "coupled,"
"connected," and the like, as generally used herein, refers to two
or more elements that may be either directly connected, or
connected by way of one or more intermediate elements.
Additionally, the words "herein," "above," "below," and words of
similar import, when used in this application, shall refer to this
application as a whole and not to any particular portions of this
application. Where the context permits, words in the above Detailed
Description using the singular or plural number may also include
the plural or singular number respectively. The word "or" in
reference to a list of two or more items, that word covers all of
the following interpretations of the word: any of the items in the
list, all of the items in the list, and any combination of the
items in the list. All numerical values provided herein are
intended to include similar values within a measurement error.
[0110] Moreover, conditional language used herein, such as, among
others, "can," "could," "might," "e.g.," "for example," "such as"
and the like, unless specifically stated otherwise, or otherwise
understood within the context as used, is generally intended to
convey that certain embodiments include, while other embodiments do
not include, certain features, elements and/or states. Thus, such
conditional language is not generally intended to imply that
features, elements and/or states are in any way required for one or
more embodiments or that one or more embodiments necessarily
include logic for deciding, with or without author input or
prompting, whether these features, elements and/or states are
included or are to be performed in any particular embodiment.
[0111] The above detailed description of embodiments is not
intended to be exhaustive or to limit the invention to the precise
form disclosed above. While specific embodiments of, and examples
for, the invention are described above for illustrative purposes,
For example, while processes or blocks are presented in a given
order, alternative embodiments may perform routines having acts, or
employ systems having blocks, in a different order, and some
processes or blocks may be deleted, moved, added, subdivided,
combined, and/or modified. Each of these processes or blocks may be
implemented in a variety of different ways. Also, while processes
or blocks are at times shown as being performed in series, these
processes or blocks may instead be performed in parallel, or may be
performed at different times.
[0112] While certain embodiments of the inventions have been
described, these embodiments have been presented by way of example
only, and are not intended to limit the scope of the disclosure.
For example, various equivalent modifications are possible within
the scope of the invention, as those skilled in the relevant art
will recognize. Moreover, the elements and acts of the various
embodiments described above can be combined to provide further
embodiments. Indeed, the methods, systems, apparatus, and articles
of manufacture described herein may be embodied in a variety of
other forms; furthermore, various omissions, substitutions and
changes in the form of the methods, systems, apparatus, and
articles of manufacture described herein may be made without
departing from the spirit of the disclosure. The accompanying
claims and their equivalents are intended to cover such forms or
modifications as would fall within the scope and spirit of the
disclosure.
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