U.S. patent number RE46,059 [Application Number 14/605,715] was granted by the patent office on 2016-07-05 for laser diode array, method of manufacturing same, printer, and optical communication device.
This patent grant is currently assigned to Sony Corporation. The grantee listed for this patent is Sony Corporation. Invention is credited to Takahiro Arakida, Osamu Maeda, Masaki Shiozaki.
United States Patent |
RE46,059 |
Maeda , et al. |
July 5, 2016 |
**Please see images for:
( Certificate of Correction ) ** |
Laser diode array, method of manufacturing same, printer, and
optical communication device
Abstract
A method of manufacturing a laser diode array capable of
inhibiting electric cross talk is provided. The method of
manufacturing a laser diode array includes a processing step of
forming a peel layer containing an oxidizable material and a
vertical resonator structure over a first substrate sequentially
from the first substrate side by crystal growth, and then
selectively etching the peel layer and the vertical resonator
structure to the first substrate, thereby processing into a
columnar shape, a peeling step of oxidizing the peel layer from a
side face, and then peeling the vertical resonator structure of
columnar shape from the first substrate, and a rearrangement step
of jointing a plurality of vertical resonator structures of
columnar shape obtained by the peeling step to a surface of a metal
layer of a second substrate formed with the metal layer on the
surface.
Inventors: |
Maeda; Osamu (Kanagawa,
JP), Shiozaki; Masaki (Kanagawa, JP),
Arakida; Takahiro (Kanagawa, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
Sony Corporation |
Tokyo |
N/A |
JP |
|
|
Assignee: |
Sony Corporation (Tokyo,
JP)
|
Family
ID: |
40382091 |
Appl.
No.: |
14/605,715 |
Filed: |
January 26, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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12219491 |
Jun 14, 2011 |
7960195 |
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Reissue of: |
13064218 |
Mar 11, 2011 |
8363689 |
Jan 29, 2013 |
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Foreign Application Priority Data
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Aug 22, 2007 [JP] |
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2007-216401 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01S
5/423 (20130101); H01S 5/18311 (20130101); H01S
5/0217 (20130101); H01S 5/1838 (20130101); H01S
5/187 (20130101); H01S 5/18341 (20130101); H01S
5/34313 (20130101); H01S 5/0425 (20130101); Y10S
438/977 (20130101); H01S 5/02345 (20210101); H01S
5/042 (20130101); H01L 2224/73267 (20130101); H01S
2304/04 (20130101); H01L 2224/24137 (20130101); H01L
2224/18 (20130101); H01S 5/0237 (20210101) |
Current International
Class: |
H01S
5/187 (20060101); H01S 5/42 (20060101); H01S
5/02 (20060101); H01S 5/183 (20060101); H01S
5/022 (20060101); H01S 5/042 (20060101) |
Field of
Search: |
;372/50.1,50.11,50.12,50.124 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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01-281786 |
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Nov 1989 |
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JP |
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11-274633 |
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Oct 1999 |
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JP |
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2003-347669 |
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Dec 2003 |
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JP |
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2005-159071 |
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Jun 2005 |
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JP |
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2005-317801 |
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Nov 2005 |
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JP |
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2006-147874 |
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Jun 2006 |
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JP |
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2008-182214 |
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Aug 2008 |
|
JP |
|
Other References
Japanese Office Action issued Jan. 26, 2012 for corresponding
Japanese Application No. 2007-216401. cited by applicant.
|
Primary Examiner: Menefee; James
Attorney, Agent or Firm: Michael Best and Friedrich LLP
Parent Case Text
CROSS REFERENCES TO RELATED APPLICATIONS
.Iadd.The present application is a reissue application of
application Ser. No. 13/064,218, now U.S. Pat. No. 8,363,689,
issued Jan. 29, 2013. .Iaddend.This is a Divisional Application of
patent application Ser. No. 12/219,491, filed Jul. 23, 2008, which
claims priority from Japanese Patent Application JP 2007-216401
filed in the Japanese Patent Office on Aug. 22, 2007, the entire
contents of which are incorporated herein by reference.
Claims
What is claimed is:
1. A laser diode array comprising: a support substrate including a
support base, a first insulating layer, an adhesive layer, and a
metal layer; a plurality of vertical resonator structures of
columnar shape jointed to a surface of the metal layer, where each
vertical resonator structure includes a first contact layer jointed
to the metal layer, a first DBR layer, a first spacer layer, an
active layer, a second spacer layer, a second DBR layer, and a
second contact layer sequentially from the metal layer side; and an
aperture formed in a second insulating layer configured to expose a
portion of the metal layer.
2. The laser diode array according to claim 1, wherein the
respective vertical resonator structures are obtained by removing a
second substrate from a structure formed by crystal growth on the
second substrate.
3. The laser diode array according to claim 1, wherein the vertical
resonator structure is made of a material different from a material
of the support substrate.
4. The laser diode array according to claim 1, wherein in the
support substrate, one or a plurality of connection parts that
penetrate a portion other than the metal layer in the support
substrate are formed to be in contact with the metal layer.
5. A printer using the laser diode array of claim 1 as a light
source.
6. An optical communication device using the laser diode array of
claim 1 as a light source.
7. The laser diode array according to claim 1, wherein a current
confinement layer is between the second spacer layer and the second
DBR layer.
8. The laser diode array according to claim 1, wherein the current
confinement layer comprises a current confinement region that is in
a peripheral region of a current injection region.
.Iadd.9. A laser diode array comprising: a support substrate
including a support base, a first insulating layer, an adhesive
layer, and a metal layer; a vertical resonator structure of
columnar shape electrically connected to the metal layer, where the
vertical resonator structure includes a first contact layer
directly connected to the metal layer, a first DBR layer, a first
spacer layer, an active layer, a second spacer layer, a second DBR
layer, and a second contact layer sequentially from the metal layer
side; and an aperture formed in a second insulating layer
configured to expose a portion of the metal layer..Iaddend.
.Iadd.10. An optical communication module comprising: the laser
diode array according to claim 9..Iaddend.
.Iadd.11. The optical communication module according to claim 10,
further comprising: a waveguide member optically coupled to the
laser diode array..Iaddend.
.Iadd.12. The laser diode array according to claim 9, wherein the
resonator structure is discretely formed from the support substrate
and jointed to the support substrate..Iaddend.
.Iadd.13. The laser diode array according to claim 9, wherein the
vertical resonator structure is made of a material different from a
material of the support substrate..Iaddend.
.Iadd.14. The laser diode array according to claim 9, wherein in
the support substrate, one or a plurality of connection parts that
penetrate a portion other than the metal layer in the support
substrate are formed to be in contact with the metal
layer..Iaddend.
.Iadd.15. A printer comprising the laser diode array of claim
9..Iaddend.
.Iadd.16. The laser diode array according to claim 9, wherein the
vertical resonator structure further includes a current confinement
layer formed between the second spacer layer and the second DBR
layer..Iaddend.
.Iadd.17. The laser diode array according to claim 9, wherein the
current confinement layer includes a current confinement region
that is in a peripheral region of a current injection
region..Iaddend.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a laser diode array including a
columnar vertical resonator structure, a method of manufacturing
the same, a printer including the laser diode array, and an optical
communication device including the laser diode array.
2. Description of the Related Art
In recent years, in the field of laser diodes (LD), a laser array
in which a plurality of Vertical Cavity Surface Emitting Lasers
(VCSEL) is formed on the same substrate has been actively
developed. The laser array is used as a light source for an optical
communication device, a laser printer and the like.
In the field of optical communication devices, the laser printers
and the like, because of downsizing, it has been desired to
propagate laser light emitted from each laser diode formed on the
same substrate by a single optical system. However, when the
distance between each laser diode is reduced, cross talk due to
heat generated from each laser diode and current leaked from each
laser diode becomes significant. As a result, interference, color
blur and the like occur.
Therefore, for example, in Japanese Unexamined Patent Application
Publication No. 11-274633, a technique in which a groove is
provided between each laser diode and a terminal section is
provided on the both ends of the groove has been proposed. In the
application, the following is represented. That is, a path to
conduct generated heat to a region other than an adjacent laser
diode is secured, and in addition to that a heat conduction path to
the adjacent laser diode is blocked. Accordingly, thermal cross
talk is decreased without deterioration of the characteristics of
each laser diode.
SUMMARY OF THE INVENTION
However, in the technique of Japanese Unexamined Patent Application
Publication No. 11-274633, it is difficult to increase the width
and the depth of the groove so much, and thus laser diodes adjacent
to each other are not able to be totally separated electrically.
Therefore, there is an issue that electric cross talk occurs.
In view of the foregoing, in the invention, it is desirable to
provide a laser diode array capable of inhibiting electric cross
talk, a method of manufacturing the same, a printer including the
laser diode array, and an optical communication device including
the laser diode array.
According to an embodiment of the invention, there is provided a
method of manufacturing a laser diode array including the following
respective steps A1 to A3: Step A1: a processing step of forming a
peel layer containing an oxidizable material and a vertical
resonator structure over a first substrate sequentially from the
first substrate side by crystal growth, and then selectively
etching the peel layer and the vertical resonator structure to the
first substrate, thereby processing into a columnar shape; Step A2:
a peeling step of oxidizing the peel layer from a side face, and
then peeling the vertical resonator structure of columnar shape
from the first substrate; and Step A3: a rearrangement step of
jointing a plurality of vertical resonator structures of columnar
shape obtained by the peeling step to a surface of a metal layer of
a second substrate formed with the metal layer on a surface.
In the method of manufacturing a laser diode array according to the
embodiment of the invention, the peel layer provided between the
first substrate and the vertical resonator structure is oxidized
from the side face. Thereby, a stress due to oxidation is generated
in the peel layer. Thus, by applying an external force to the peel
layer, the vertical resonator structure is easily peeled from the
first substrate. After that, the plurality of columnar vertical
resonator structures obtained by the peeling step is jointed to the
surface of the metal layer of the second substrate. Thereby, a
resistance component of the first substrate that is connected in
series to each vertical resonator structure is separated from each
vertical resonator structure.
According to an embodiment of the invention, there is provided a
laser diode array including a first substrate in which a metal
layer is formed on a surface thereof and a plurality of vertical
resonator structures of columnar shape. The respective vertical
resonator structures are jointed to a surface of the metal layer.
According to embodiments of the invention, there are provided a
printer and an optical communication device using the foregoing
laser diode array as a light source.
In the laser diode array, the printer, and the optical
communication device according to the embodiments of the invention,
the respective vertical resonator structures are jointed to the
surface of the metal layer. Therefore, a resistance component of
the common substrate that is connected in series to each vertical
resonator structure (common substrate used for forming each
vertical resonator structure) is separated from each vertical
resonator structure.
According to the method of manufacturing a laser diode array of the
embodiment of the invention, the plurality of columnar vertical
resonator structures peeled from the first substrate with the use
of oxidation of the peel layer is jointed to the surface of the
metal layer of the second substrate. Thus, the resistance component
of the first substrate that is connected in series to each vertical
resonator structure is separated from each vertical resonator
structure. Thereby, electric cross talk generated when the
plurality of vertical resonator structures are formed on the common
substrate is inhibited from being generated.
According to the laser diode array, the printer, and the optical
communication device, of the embodiments of the invention, the
respective vertical resonator structures are jointed to the surface
of the metal layer. Therefore, the resistance component of the
common substrate that is connected in series to each vertical
resonator structure is separated from each vertical resonator
structure. Thereby, electric cross talk generated when the
plurality of vertical resonator structures are formed on the common
substrate is inhibited from being generated.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a top view of a laser diode array according to an
embodiment of the invention;
FIG. 2 is across section view taken along arrows A-A of the laser
diode array of FIG. 1;
FIGS. 3A and 3B are cross section views for explaining an example
of a method of manufacturing the laser diode array of FIG. 1;
FIGS. 4A and 4B are cross section views for explaining steps
following FIGS. 3A and 3B;
FIG. 5 is a top view for explaining a step following FIGS. 4A and
4B;
FIG. 6 is a cross section view taken along arrows A-A of FIG.
5;
FIG. 7 is an equivalent circuit diagram of the laser diode array of
FIG. 1;
FIGS. 8A and 8B are waveform charts of a CW waveform and a pulse
waveform inputted to the laser diode array of FIG. 1;
FIGS. 9A and 9B are cross section views for explaining another
example of a method of manufacturing the laser diode array of FIG.
1;
FIGS. 10A and 10B are cross section views for explaining steps
following FIGS. 9A and 9B;
FIGS. 11A and 11B are cross section views for explaining steps
following FIGS. 10A and 10B;
FIGS. 12A and 12B are cross section views for explaining steps
following FIGS. 11A and 11B;
FIG. 13 is a top view of a modification of the laser diode array of
FIG. 1;
FIG. 14 is a cross section view taken along arrows A-A of the laser
diode array of FIG. 13;
FIG. 15 is a schematic structural view of a printer according to an
application example;
FIG. 16 is a schematic structural view of an optical communication
device according to another application example;
FIG. 17 is a cross section view of a laser diode array of a related
art;
FIG. 18 is an equivalent circuit diagram of the laser diode array
of FIG. 11; and
FIGS. 19A and 19B are waveform charts for explaining cross talk in
the laser diode array of FIG. 11.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Descriptions will be given of an embodiment of the invention in
detail with reference to the drawings.
FIG. 1 shows a top view of a laser diode array 1 according to an
embodiment of the invention. FIG. 2 shows a cross sectional
configuration taken along arrows A-A of the laser diode array 1 of
FIG. 1. FIG. 1 and FIG. 2 schematically show the laser diode array
1, and the dimensions and the shapes in the figures are different
from those actually used.
The laser diode array 1 includes a plurality of Vertical Cavity
Surface Emitting Laser (VCSEL) devices 20 (vertical resonator
structure) on a support substrate 10. The laser diode array 1 has a
function to concurrently output a plurality of laser lights having
the same wavelength.
Further, in the laser diode array 1, the plurality of laser diode
devices 20 is arranged on the surface on a metal layer 14
(described later) side of the support substrate 10, so that the
distance P between each optical axis AX of each laser light emitted
from each laser diode device 20 is as short as possible. For
example, as shown in FIG. 1, the respective laser diode devices 20
are arranged in a lattice pattern at almost even intervals.
However, the laser diode devices 20 are not necessarily arranged in
a vertical and reticular pattern at almost even intervals, but they
may be, for example, arranged in a line at almost even
intervals.
Support Substrate 10
The support substrate 10 has, for example, a support base 11, an
insulating layer 12, an adhesive layer 13, the metal layer 14, a
via 15 (connection part), and an electrode layer 16. The insulating
layer 12, the adhesive layer 13, and the metal layer 14 are layered
in this order from the support base 11 side on one face side of the
support base 11. The electrode layer 16 is formed on the other face
side of the one face of the support base 11. The via 15 is formed
to penetrate through the support base 11, the insulating layer 12,
and the adhesive layer 13. One end thereof is in contact with the
lower face of the metal layer 14, and the other end thereof is in
contact with the top face of the electrode layer 16.
The support base 11 is made of a material different from that of
the laser diode device 20. The support base 11 is made of, for
example, a silicon substrate. The insulating layer 12 is made of an
insulative material such as silicon oxide (SiO.sub.2) and silicon
nitride (SiN). The adhesive layer 13 is made of, for example,
multicrystalline silicon, amorphous silicon or the like. The
multicrystalline silicon and the amorphous silicon have a high
affinity with the insulative material, such as silicon oxide
(SiO.sub.2) and silicon nitride (SiN). Thus, when the insulative
material such as silicon oxide (SiO.sub.2) and silicon nitride
(SiN) is used as the insulating layer 12 and the multicrystalline
silicon or the amorphous silicon is used as the adhesive layer 13,
the contact characteristics between the insulating layer 12 and the
adhesive layer 13 become strong.
Laser Diode Device 20
The laser diode device 20 is joined to the metal layer 14 of the
support substrate 10. The laser diode device 20 has a columnar
vertical resonator structure in which, for example, a lower contact
layer 21, a lower DBR layer 22, a lower spacer layer 23, an active
layer 24, an upper spacer layer 25, a current confinement layer 26,
an upper DBR layer 27, and an upper contact layer 28 are layered in
this order from the metal layer 14 side. That is, the laser diode
device 20 is obtained by removing a separately prepared
semiconductor substrate 40 (described later) from a structure in
which the foregoing vertical resonator structure is formed by
crystal growth on the semiconductor substrate 40.
The lower contact layer 21 is made of, for example, n-type
Al.sub.x1Ga.sub.1-x1As (0.ltoreq.x1<1). The lower DBR layer 22
is formed by alternately layering a low refractive index layer (not
shown) and a high refractive index layer (not shown). The low
refractive index layer is made of, for example, n-type
Al.sub.x2Ga.sub.1-x2As (0<x2<1) having an optical thickness
of .quadrature..sub.1/4 (.quadrature..sub.1 is an oscillation
wavelength). The high refractive index layer is made of, for
example, n-type Al.sub.x3Ga.sub.1-x3As (0.ltoreq.x3<x2) having
an optical thickness of .quadrature..sub.1/4. The lower spacer
layer 23 is made of, for example, n-type Al.sub.x4Ga.sub.1-x4As
(0.ltoreq.x4<2). The lower contact layer 21, the lower DBR layer
22, and the lower spacer layer 23 contain a n-type impurity, such
as silicon (Si).
The active layer 24 has a multi-quantum well structure in which it
well layer (not shown) made of undoped In.sub.x5Ga.sub.1-x5As
(0<x5<1) and a barrier layer (not shown) made of undoped
In.sub.x6Ga.sub.1-x6N (0<x6<x5) are alternately layered. Of
the active layer 24, the region opposed to a current injection
region 26A (described later) is a light emitting region 24A.
The upper spacer layer 25 is made of, for example, p-type
Al.sub.x7Ga.sub.1-x7As (0.ltoreq.x7<1). The upper DBR layer 27
is formed by alternately layering a low refractive index layer (not
shown) and a high refractive index layer (not shown). The low
refractive index layer is made of, for example, p-type
Al.sub.x8Ga.sub.1-x8As (0<x8<1) having an optical thickness
of .quadrature..sub.1/4. The high refractive index layer is made
of, for example, p-type Al.sub.9Ga.sub.1-x9N (0.ltoreq.x9<x8)
having an optical thickness of .quadrature..sub.1/4. The upper
contact layer 28 is made of, for example, p-type
Al.sub.x10Ga.sub.1-x10N (0.ltoreq.x10<1). The upper spacer layer
25, the upper DBR layer 27, and the upper contact layer 28 include
a p-type impurity, such as magnesium (Mg).
The current confinement layer 26 has a current confinement region
26B in the peripheral region of a current injection region 26A.
The current injection region 26A is made of, for example, p-type
Al.sub.x11Ga.sub.1-x11As (0<x11.ltoreq.1). The current injection
region 26A is preferably made of a material having an oxidation
rate equal to or slower than that of a peel layer 41D described
later.
For example, when the peel layer 4D is made of AlAs, the current
injection region 26A is made of Al.sub.x11Ga.sub.1-x11As
(0.98.ltoreq.x11.ltoreq.1). In the case where the current injection
region 26A is made of AlAs (x11=1), the thickness of the current
injection region 26A needs to be smaller than the thickness of the
peel layer 41D. Meanwhile, when the current injection region 26A is
made of Al.sub.x11Ga.sub.1-x11As (0.98.ltoreq.x11<1), the
thickness of the current injection region 26A may be equal to or
smaller than the thickness of the peel layer 41D. However, as will
be described later, when the oxidation step of the peel layer 41D
is performed separately from the oxidation step of the current
confinement layer 26D, the material of the current injection region
26A is not particularly limited in relation to the peel layer
41D.
Meanwhile, the current confinement region 26B contains, for
example, Al.sub.2O.sub.3 (aluminum oxide). As will be described
later, the current confinement region 26B is obtained by oxidizing
concentrated Al contained in a current confinement layer 26D from
the side face. Therefore, the current confinement layer 26 has a
function of confining a current.
In the laser diode device 20 of this embodiment, a circular
electrode layer 30 is formed on the top face of the upper contact
layer 28. The electrode layer 30 is formed by layering, for
example, a Ti layer, a Pt layer, and an Au layer in this order. The
electrode layer 30 is electrically connected to the upper contact
layer 28.
Further, an insulating film 31 is formed over the entire surface
including each laser diode device 20 and the electrode layer 30.
The insulating film 31 is made of an insulative material, such as
silicon oxide (SiO.sub.2) and silicon nitride (SiN). An aperture is
formed in part of the region opposed to the electrode layer 30 of
the insulating film 31. An electrode pad 33 electrically connected
to a wiring layer 32 through the aperture is formed on the surface
of the insulating film 31 (refer to FIG. 1).
The laser diode array 1 having the foregoing configuration may be
manufactured as follows, for example.
First, the laser diode device 20 is manufactured. For example, in
the case where the vertical resonator structure is formed from
GaAs-based Group III-V compound semiconductor, for example, the
vertical resonator structure is formed by the Metal Organic
Chemical Vapor Deposition (MOCVD) method with the use of TMA
(trimethyl aluminum), TMG (trimethyl gallium), TMIn (trimethyl
indium), or AsH.sub.3 (arsine) its a raw material gas.
The GaAs-based Group III-V compound semiconductor represents a
semiconductor that contains at least Ga out of the Group 3B
elements in the short period periodic table and at least As
(arsenic) out of the Group 5B elements in the short period periodic
table.
Specifically, the peel layer 41D, the lower contact layer 21, the
lower DBR layer 22, the lower spacer layer 23, the active layer 24,
the upper spacer layer 25, the current confinement layer 26D (layer
to be oxidized), the upper DBR layer 27, and the upper contact
layer 28 are layered in this order over the semiconductor substrate
40 (GaAs substrate) (FIG. 3A).
The foregoing current confinement layer 26D is made of the same
material as that of the current injection region 26A, and will
become the current confinement layer 26 by the after-mentioned
oxidation treatment. The peel layer 41D is preferably structured to
have a faster oxidation rate in the lamination in-plane direction
than that of the current confinement layer 26D.
For example, in the case where the current confinement layer 26D is
made of the same material as that of the peel layer 41D (for
example, Al.sub.x11Ga.sub.1-x11As (0.98<x11.ltoreq.1), the
thickness of the peel layer 41D is preferably larger than that of
the current confinement layer 26D. In the case where the current
confinement layer 26D is made of Al.sub.x11Ga.sub.1-x11As
(0.98<x11<1), the peel layer 41D is preferably made of AlAs.
In the case where the current confinement layer 26D is made of
Al.sub.x11Ga.sub.1-x11As (0.98<x11<1) and the peel layer 41D
is made of AlAs, that is, when the peel layer 41D is made of a
material having a faster oxidation rate than that of the current
confinement layer 26D, the thickness of the peel layer 41D may be
equal to or larger than the thickness of the current confinement
layer 26D.
Next, a region from the upper contact layer 28 to part of the
semiconductor substrate 40 is selectively etched by, for example,
the dry etching method to form a mesa shape (FIG. 3B). Thereby, the
peel layer 41D is exposed on the side face of a mesa M.
Next, heat treatment is performed at high temperature in a water
vapor atmosphere, and the current confinement layer 26D and the
peel layer 41D are concurrently oxidized from the side face of the
mesa M. The oxidation treatment is performed until almost all of
the peel layer 41D is oxidized and the diameter of the non-oxidized
region of the current confinement layer 26D becomes a desired
value. Thereby, almost all of the peel layer 41D becomes an
insulating layer (alumninum oxide), and an oxidized peel layer 41
is formed (FIG. 4A). Further, since the outer edge region of the
current confinement layer 26D becomes an insulating layer (aluminum
oxide), the current confinement region 26B is formed in the outer
edge region, and the current injection region 26A is formed in the
central region thereof. Accordingly, the laser diode device 20 is
formed over the semiconductor substrate 40 (FIG. 4A).
Next, for example, the laser diode device 20 is peeled from the
semiconductor substrate 40 by, for example, vacuum contact or by
using a light curable adhesive sheet or the like (FIG. 4B. Out of
the interfaces between each layer composing the laser diode device
20, at the interface between the oxidized peel layer 41 and the
lower contact layer 21, the oxidized peel layer 41 and the lower
contact layer 21 are not contacted with each other in a graded
manner. That is, at the interface between the oxidized peel layer
41 and the lower contact layer 21, an interlayer in which the both
materials are mixed with each other does not exist. Otherwise, even
if such an interlayer exists, the interlayer slightly exists to the
degree that the interlayer is ignorable compared to the thickness
of interlayer at the other interfaces. Thus, since a stress caused
by oxidation has been applied to the interface between the oxidized
peel layer 41 and the lower contact layer 21, the laser diode
device 20 is able to be relatively easily peeled at the interface
between the oxidized peel layer 41 and the lower contact layer 21
or in the vicinity thereof by the peeling step.
Heating (alloying) may be performed at about from 300 deg C. to 400
deg C. before the peeling step. In this case, the stress at the
interface between the oxidized peel layer 41 and the lower contact
layer 21 is further increased, and thus the laser diode device 20
is able to be easily peeled. If the oxidized peel layer 41 remains
on the laser diode device 20 side, the portion of the oxidized peel
layer 41 remaining on the laser diode device 20 side is removed by
wet etching.
Next, the plurality of laser diode devices 20 is arranged with the
lower contact layer 21 side downward on the metal layer 14 of the
support substrate 10 and jointed to the metal layer 14 (FIG. 5 and
FIG. 6). FIG. 6 is a cross sectional configuration view takes along
arrows A-A of FIG. 5.
Next, the circular electrode layer 30 is formed on the top face of
the laser diode device 20 (FIG. 2). Subsequently, the insulating
film 31 is formed over the entire surface including the laser diode
device 20 and the electrode layer 30. After that, the electrode pad
33 is formed in a place with a given distance from the laser diode
20 in the surface of the insulating film 31. After that, the
aperture (not shown) is formed in part of the region opposed to the
electrode layer 30 in the insulating film 31. After that, the
wiring layer 32 extending from the surface of the electrode layer
30 exposed in the aperture to the electrode pad 33 is formed.
Accordingly, the laser diode array 1 of this embodiment is
manufactured.
In the laser diode array 1 of this embodiment, when a given voltage
is applied between the connection pad 33 electrically connected to
the electrode layer 30 on each laser diode device 20 and the
electrode layer 16, a current is injected into the active layer 24,
light emission is generated by electron-hole recombination, and
stimulated emission is repeated in the device. As a result, laser
oscillation is generated in a given wavelength .quadrature..sub.1,
and laser light in wavelength .quadrature..sub.1 is outputted
outside from the light emitting region 24A of each laser diode
device 20 through the aperture of the electrode layer 30.
In a laser diode array 100 of the related art shown in FIG. 17,
that is, in the laser array in which a columnar VCSEL 120 obtained
by layering, for example, a lower DBR layer 121, a lower spacer
layer 122, an active layer 123, an upper spacer layer 124, a
current confinement layer 125 (current injection region 125A and a
current confinement region 125B), an upper DBR layer 126, and an
upper contact layer 127 in this order over a common substrate 110
is directly formed by crystal growth, as shown in the equivalent
circuit shown in FIG. 18, a resistance component R3 exists between
each laser diode 120 and a ground GND independently of a current
path of other laser diode 120, and a resistance component R4 exists
on the current path common to each laser diode 120.
The resistance component R4 is a resistance component of the common
substrate 110. In the case where the resistance component R4
exists, for example, when one laser diode device 120 is CW-driven
as shown in FIG. 8A and another laser diode device 120 adjacent to
the foregoing one laser diode device 120 is pulse-driven as shown
in FIG. 8B, in the equivalent circuit of FIG. 18, an input voltage
V.sub.L1 of the CW-driven laser diode device 120 has a wavy
waveform including noise as shown in FIG. 19A, and an input voltage
V.sub.L2 of the pulse-driven laser diode device 120 has a distorted
rectangular waveform including noise as shown in FIG. 19B. That is,
electric cross talk is generated between the laser diode devices
120 adjacent to each other.
Meanwhile, in this embodiment, each laser diode device 20 is
jointed to the surface of the metal layer 14 of the support
substrate 10. Thus, as shown in FIG. 7, in the equivalent circuit
of the laser diode array 1, the resistance component R3 exists
between each laser diode device 20 and the ground GND independently
of a current path of the other laser diode device 20, but no
resistance component exists on the current path common to each
laser diode device 20. This is because, in the manufacturing course
of this embodiment, the semiconductor substrate 40 is removed
(peeled) from the structure in which the vertical resonator
structure is formed by crystal growth over the semiconductor
substrate 40, and thereby the resistance component of the
semiconductor substrate 40 that is connected in series to each
vertical resonator structure is separated from each vertical
resonator structure.
Thereby, for example, in the case where one laser diode device 20
is CW-driven as shown in FIG. 8A and another laser diode device 20
adjacent to the foregoing one laser diode device 20 is pulse-driven
as shown in FIG. 8B, in the equivalent circuit of FIG. 7, the input
voltage V.sub.L1 of the CW-driven laser diode device 20 has a flat
waveform not including noise as an input voltage waveform, and the
input voltage V.sub.L2 of the pulse-driven laser diode device 20
has a rectangular waveform not including noise as the input voltage
waveform. That is, electric cross talk is not generated between the
laser diode devices 20 adjacent to each other.
As described above, in this embodiment, since each laser diode
device 20 is jointed to the surface of the metal layer 14 of the
support substrate 10, the resistance component of the semiconductor
substrate 40 that is connected in series to each laser diode device
20 is separated from each laser diode device 20. Thereby, electric
cross talk between the laser diode devices 20 adjacent to each
other is inhibited from being generated.
Modification
In the foregoing embodiment, the oxidation steps of the peel layer
41D and the current confinement layer 26D are concurrently
performed. However, each oxidation step may be performed
separately. For example, it is possible that after the side face of
the current confinement layer 26D is coated with a protective film
so that the side face of the peel layer 41D is not coated
therewith, the oxidized peel layer 41 is formed by oxidizing the
peel layer 41D from the side face, the protective film is removed,
and then the current confinement layer 26D is oxidized from the
side face to form the current confinement layer 26.
Further, the formation step of the laser diode device 20 may be
performed, for example, as follows. First, the peel layer 41D, the
lower contact layer 21, the lower DBR layer 22, the lower spacer
layer 23, the active layer 24, the upper spacer layer 25, the
current confinement layer 26D (layer to be oxidized), the upper DBR
layer 27, and the upper contact layer 28 are layered in this order
over the semiconductor substrate 40 (GaAs substrate) (FIG. 3A).
Then, a region from the upper contact layer 28 to part of the lower
DBR layer 22 is selectively etched by, for example, a dry etching
method to form a mesa shape.
Next, heat treatment is performed at a high temperature in the
water vapor atmosphere, the current confinement layer 26D is
oxidized from the side face of the mesa M to form the current
confinement layer 26 (FIG. 9B). Since the peel layer 41D is not
exposed on the side face of the mesa M, the peel layer 41D is not
oxidized.
Next, a protective film 19 is formed on the entire surface
including the mesa M (FIG. 10A). After that, a groove 29A
penetrating thorough the protective film 19 is formed to surround
the mesa M (FIG. 10B). Thereby, the lower DBR layer 22 is exposed
on the bottom face of the groove 29A.
Next, for example, the lower DBR layer 22 and the lower contact
layer 21 that are directly under the groove 29A are selectively
removed by using, for example, a phosphoric acid etchant (FIG.
11A). After that, the peel layer 41D is selectively removed by
using a fluorinated acid etchant (FIG. 11B). Thereby, the contact
force by the peel layer 41D between the semiconductor substrate 40
and the lower DBR layer 22 is lowered.
Next, a support substrate 42 is bonded to the top face of the
protective film 19 (FIG. 12A). After that, by using the support
substrate 42, the laser diode device 20 is peeled from the
semiconductor substrate 40 (FIG. 12B). Accordingly, the laser diode
device 20 is able to be formed as well.
In the foregoing embodiment, the VCSEL 20 is jointed to the surface
of the metal layer 14 of the support substrate 10 having the via
15. However, for example, as shown in FIG. 13 and FIG. 14, it is
possible that a support substrate 50 in which the insulating layer
12, the adhesive layer 13, and the metal layer 14 are sequentially
layered from the support base 11 side is prepared on one surface of
the support base 11, and the VCSEL 20 is jointed to the surface of
the metal layer 14 of the support substrate 50. However, in this
case, for example, it is necessary that an aperture 31A is formed
in part of the insulating layer 31 formed on the surface of the
metal layer 14, part of the metal layer 14 is exposed from the
aperture, and the exposed section is used as an electrode pad 14A
to decrease the potential of the metal layer 14 to the ground
potential.
Further, in the foregoing embodiment, the wiring layer 32 and the
electrode pad 33 are formed over the support substrate 10 with the
insulating layer 31 in between. However, for example, it is
possible to provide a buried layer made of an insulative material,
such as polyimide, around the laser diode device 20, the wiring
layer 32 and the electrode pad 33 that are formed on the top face
of the buried layer, and thereby the capacity component generated
between the wiring layer 32 electrode pad 33 and the metal layer 14
is decreased as much as possible.
Application Example
The laser diode array 1 according to the foregoing embodiment or
the modification thereof is suitably applicable to, for example, a
printer, such as a laser printer, and an optical communication
device, such as a multichannel optical integrated device. For
example, as shown in FIG. 15, as a light source 61 in a laser
printer 60 including the light source 61, a polygon mirror 62 for
reflecting light from the light source 61 and scanning the
reflected light, a f.quadrature. lens 63 for guiding the light from
the polygon mirror 62 to a photoconductive drum 64, the
photoconductive drum 64 receiving the light from the f.quadrature.
lens 63 to form an electrostatic latent image, and a toner supplier
(not shown) adhering the toner according to the electrostatic
latent image to the photoconductive drum 64, the laser diode array
1 may be used. Further, for example, as shown in FIG. 16, as a
light source 72 in art optical communication device 70 including
the light source 72, a light guide 73 in which a light input end is
arranged correspondingly to a light output end of the light source
72, and an optical fiber 74 in which a light input end is provided
correspondingly to a light output end of the light guide 73 on a
support substrate 71, the laser diode array 1 may be used.
While the descriptions hereinbefore have been given of the
invention with reference to the embodiment and the like, the
invention is not limited to the foregoing embodiment and the like,
and various modifications may be made.
It should be understood by those skilled in the art that various
modifications, combinations, subcombinations and alternations may
occur depending on design requirements and other factors insofar as
they are within the scope of the appended claims or the equivalents
thereof.
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