U.S. patent application number 17/573701 was filed with the patent office on 2022-05-05 for semiconductor laser diode.
The applicant listed for this patent is OSRAM OLED GmbH. Invention is credited to Wolfgang Reill.
Application Number | 20220140566 17/573701 |
Document ID | / |
Family ID | 1000006079173 |
Filed Date | 2022-05-05 |
United States Patent
Application |
20220140566 |
Kind Code |
A1 |
Reill; Wolfgang |
May 5, 2022 |
SEMICONDUCTOR LASER DIODE
Abstract
A semiconductor laser diode includes a semiconductor body having
an emitter region; and a first connection element that electrically
contacts the semiconductor body in the emitter region, wherein the
semiconductor body is in contact with the first connection element
in the emitter region, at least in places in the emitter region,
the semiconductor body has a structuring that enlarges a contact
area between the semiconductor body and the first connection
element, the semiconductor body includes a connection region that
directly adjoins the first connection element at the contact area,
and the connection region is a highly p-doped layer.
Inventors: |
Reill; Wolfgang; (Pentling,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
OSRAM OLED GmbH |
Regensburg |
|
DE |
|
|
Family ID: |
1000006079173 |
Appl. No.: |
17/573701 |
Filed: |
January 12, 2022 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16308985 |
Dec 11, 2018 |
11245246 |
|
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PCT/EP2017/063208 |
May 31, 2017 |
|
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17573701 |
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Current U.S.
Class: |
372/43.01 |
Current CPC
Class: |
H01S 5/0234 20210101;
H01S 5/04254 20190801; H01S 5/023 20210101; H01S 5/0233 20210101;
H01S 5/0653 20130101; H01S 5/02469 20130101; H01S 5/0235 20210101;
H01S 5/02461 20130101; H01S 5/0237 20210101; H01S 2301/176
20130101 |
International
Class: |
H01S 5/0237 20060101
H01S005/0237; H01S 5/042 20060101 H01S005/042; H01S 5/065 20060101
H01S005/065; H01S 5/023 20060101 H01S005/023; H01S 5/0233 20060101
H01S005/0233; H01S 5/0234 20060101 H01S005/0234; H01S 5/0235
20060101 H01S005/0235 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 13, 2016 |
DE |
10 2016 110 790.5 |
Claims
1. A semiconductor laser diode comprising: a semiconductor body
having an emitter region; and a first connection element that
electrically contacts the semiconductor body in the emitter region,
wherein the semiconductor body is in contact with the first
connection element in the emitter region, at least in places in the
emitter region, the semiconductor body has a structuring that
enlarges a contact area between the semiconductor body and the
first connection element, the semiconductor body comprises a
connection region that directly adjoins the first connection
element at the contact area, and the connection region is a highly
p-doped layer.
2. The semiconductor laser diode according to claim 1, wherein, the
connection region is not completely pierced at any point.
3. The semiconductor laser diode according to claim 1, wherein the
dopant concentration of the highly p-doped layer is at least
5*10.sup.18/cm.sup.3.
4. The semiconductor laser diode according to claim 1, wherein the
semiconductor body is thicker in the connection region than in
neighboring regions.
5. The semiconductor laser diode according to claim 1, wherein the
semiconductor body comprises a subregion arranged laterally
adjacent to the emitter region, at least in places in the
subregion, the semiconductor body has a further structuring
comprising further structures, and the further structuring is
configured to weaken secondary modes.
6. The semiconductor laser diode according to claim 5, structures
of the structuring have a mean height that is smaller than a mean
height of the further structures of the further structuring.
7. The semiconductor laser diode according to claim 5, wherein the
connection region extends in the subregion.
8. The semiconductor laser diode according to claim 7, wherein the
further structures of the further structuring completely pierce the
connection region.
9. The semiconductor laser diode according to claim 1, wherein the
structuring has a density of structures, and the density of the
structures increases towards a radiation exit surface.
10. The semiconductor laser diode according to claim 1, wherein, at
least in places, the contact area having the structuring located
between the semiconductor body and the first connection element is
at least 1.5 times as large as a contact area free of the
structuring and located between the semiconductor body and the
connection element.
11. The semiconductor laser diode according to claim 1, wherein the
connection element comprises a metallic layer that completely
covers the semiconductor body in the emitter region.
12. The semiconductor laser diode according to claim 1, wherein, at
least in places, the structuring comprises at least one structure
selected from the group consisting of truncated cone, inverse
truncated cone, truncated pyramid, inverse truncated pyramid, cone,
inverse cone, pyramid, inverse pyramid, spherical shell and inverse
spherical shell.
13. The semiconductor laser diode according to claim 1, wherein a
maximum lateral extension of each structure is at least 400 nm.
14. The semiconductor laser diode according to claim 5, wherein an
electrically insulating insulation element is arranged between the
subregion and the first connection element and in the subregion
completely covers the semiconductor body on a side facing the first
connection element.
Description
RELATED APPLICATIONS
[0001] This is a continuation of U.S. Ser. No. 16/308,985, filed
Dec. 11, 2018, which is a 371 of International Application No.
PCT/EP2017/063208, with an international filing date of May 31,
2017 (WO 2017/215919 A1, published Dec. 21, 2017), which is based
on German Patent Application No. 10 2016 110 790.5, filed Jun. 13,
2016.
TECHNICAL FIELD
[0002] This disclosure relates to a semiconductor laser diode.
BACKGROUND
[0003] WO 2013/079346 A1 describes a semiconductor laser diode.
There is nonetheless a need to provide a semiconductor laser diode
that can be used to generate laser radiation having reduced beam
divergence and a semiconductor laser diode by which laser radiation
can be generated particularly efficiently.
SUMMARY
[0004] I provide a semiconductor laser diode including a
semiconductor body having an emitter region; and a first connection
element that electrically contacts the semiconductor body in the
emitter region, wherein the semiconductor body is in contact with
the first connection element in the emitter region, at least in
places in the emitter region, the semiconductor body has a
structuring that enlarges a contact area between the semiconductor
body and the first connection element, the semiconductor body
includes a connection region that directly adjoins the first
connection element at the contact area, and the connection region
is a highly p-doped layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 illustrates in detail a problem that is solved by my
semiconductor laser diodes.
[0006] FIGS. 2 and 3 show schematic sectional views of examples of
semiconductor laser diodes.
[0007] FIG. 4 shows a schematic representation of an example of a
semiconductor laser diode.
[0008] FIGS. 5A, 5B, 5C and 5D illustrate schematic representations
of the structurings occurring in the examples of the semiconductor
laser diodes.
[0009] FIGS. 6A and 6B show schematic views of intermediate
products of the examples of semiconductor laser diodes.
LIST OF REFERENCE SIGNS
[0010] 1 carrier [0011] 2 semiconductor body [0012] 21 n-conductive
region [0013] 22 p-conductive region [0014] 23 active region [0015]
24 connection region [0016] 26 structuring [0017] 26a structure
[0018] 27 further structuring [0019] 27a further structures [0020]
28 contact area [0021] 3 first connection element [0022] 4 second
connection element [0023] 41 contact point [0024] 42 contact wire
[0025] 5 emitter region [0026] 6 subregion [0027] 7 radiation exit
surface [0028] 8 insulation element [0029] T1, T2, T3 temperatures
[0030] d distance [0031] D diameter
DETAILED DESCRIPTION
[0032] My semiconductor laser diode may comprise a semiconductor
body having an emitter region.
[0033] The semiconductor body of the semiconductor laser diode is
formed, for example, from a III-V compound semiconductor material
or from a II-VI compound semiconductor material. For example, the
semiconductor body can be epitaxially grown on a substrate.
[0034] Laser radiation is generated in the emitter region of the
semiconductor body during operation of the semiconductor laser
diode. For example, the emitter region extends over a main part of
the length of the semiconductor laser diode and includes an active
region of the semiconductor body. The active region includes, for
example, a pn-junction, a double hetero-structure, a single quantum
well structure and/or a multiple quantum well structure. The
semiconductor laser diode can have one or several emitter regions.
In particular, it is possible for the semiconductor laser diode to
have two or more emitter regions, for example, exactly five emitter
regions spaced apart in a lateral direction perpendicular to the
main extension direction of the emitter regions and arranged
parallel to each other. The lateral directions are those directions
running parallel to a main extension plane of the semiconductor
laser diode and the semiconductor body.
[0035] Within the emitter region, the semiconductor body may be
formed to be thicker in a vertical direction perpendicular to the
lateral directions than outside the emitter region. The emitter
region, for example, is then formed as a bar-shaped structure of
the semiconductor body. In particular, in the emitter region, it is
possible that the semiconductor body is electrically conductively
contacted on one side, for example, on its p-conducting side,
whereas on the same side, it is not electrically conductively
contacted outside the emitter region.
[0036] The semiconductor laser diode may comprise a first
connection element that electrically contacts the semiconductor
body in the emitter region. For example, the first connection
element is a metallic layer or a metallic layer sequence that can,
for example, directly or indirectly adjoin the semiconductor body
in the emitter region. The first connection element can cover a
main part or all of a main surface of the semiconductor body,
wherein an electrical contact is present between the first
connection element and the emitter region, in particular
exclusively in the emitter region.
[0037] In the emitter region, the semiconductor body may be in
contact with the first connection element. In particular, it is
possible for the semiconductor body to be in direct contact with
the first connection element in the emitter region. It is also
possible that the semiconductor body is in direct contact with the
first connection element only in the emitter region and there is no
direct contact between the semiconductor body and the connection
element outside the emitter region.
[0038] At least in places in the emitter region, the semiconductor
body may have a structuring that enlarges a contact area between
the semiconductor body and the first connection element. In other
words, in the emitter region on its side facing towards the first
connection element, the semiconductor body is not planar and not
flat, but has a structuring so that a contact area in which the
semiconductor body and the first connection element are in contact
with one another is enlarged compared to an unstructured
semiconductor body. The structuring can comprise a plurality of
structures formed, for example, by elevations and/or depressions in
the semiconductor body.
[0039] A semiconductor laser diode may be provided with
[0040] a semiconductor body comprising an emitter region, and
[0041] a first connection element that electrically contacts the
semiconductor body in the emitter region, wherein
[0042] in the emitter region, the semiconductor body is in contact
with the first connection element, and
[0043] at least in places in the emitter region, the semiconductor
body has a structuring that enlarges a contact area between the
semiconductor body and the first connection element.
[0044] During operation of the semiconductor laser diode, laser
radiation having a wavelength of at least 970 nm, for example, of
975 nm or 980 nm, is generated in the emitter region. The
semiconductor body of the semiconductor laser diode is based, for
example, on an InGaAs material system. The semiconductor laser,
however, can also be a semiconductor laser that generates
electromagnetic radiation in the spectral range from UV radiation
to infrared radiation and is based on a correspondingly suitable
material system, in particular on a III-V compound semiconductor
material.
[0045] The theory behind the semiconductor laser described here are
inter alia the following: One reason for high beam divergences of
the electromagnetic radiation generated by a semiconductor laser
during operation is self-focusing within a resonator of the
semiconductor laser. This self-focusing results from formation of a
thermal lens. The wave-front of the generated electromagnetic
radiation is deformed as it passes through an area with
inhomogeneous temperature distribution. In particular, towards a
light exit surface, the semiconductor laser diode heats up at a
higher rate compared to a side of the resonator of the
semiconductor laser diode facing away from the light exit side and
comprises for instance a highly reflective mirror facet. Due to the
temperature dependence of the refractive index of the semiconductor
material of the semiconductor body and the optical gain of the
semiconductor material of the semiconductor body, the thermal lens
is formed and reduces the optical gain of the semiconductor laser
diode. Furthermore, the beam divergence of the generated laser
radiation increases, resulting in a particular disadvantage
regarding coupling the laser radiation into a glass fiber, for
example.
[0046] The semiconductor laser diode is based, inter alia, on the
knowledge that an enlargement in the contact area between the
semiconductor body and the first connection element improves heat
dissipation from the semiconductor laser diode during operation
since in this way the area is enlarged through which heat is
dissipated from the semiconductor laser diode. This can be achieved
by introducing a structuring of the semiconductor body in the
emitter region without changing the geometries determining the
semiconductor laser diode such as resonator length and width. Due
to the structuring, at least in the emitter region, the
semiconductor laser diode is cooled more efficiently compared to an
unstructured semiconductor body and, during operation, the
temperature of the semiconductor laser diode can be lowered
especially in the region in which the thermal lens mentioned above
occurs.
[0047] At least in places, the contact area with the structuring
between the semiconductor body and the first connection element may
be at least 1.5 times as large as a contact area without any
structuring between the semiconductor body and the connection
element. In other words, in addition to their base area, the
structures used to form the structuring have a lateral surface that
enlarges the contact area accordingly. If, for example, the
structure is a truncated cone, depending on the height of the
truncated cone, it is possible to double the base area so that
approximately twice the amount of heat per unit area can be
dissipated.
[0048] The connection element may comprise a metallic layer that
completely covers the semiconductor body in the emitter region. For
example, it is possible that the connection element contains the
metallic layer or consists of the metallic layer. The metallic
layer can, for example, be formed by a metal that conducts heat
well such as gold, or it can consist of this metal. The metallic
layer can be applied onto the semiconductor body in particular by
sputtering or vapor deposition and in this way completely wet the
structures of the structuring so that a contiguous metallic layer
is formed on the contact area.
[0049] The structuring may comprise at least in places at least one
of the following structures: truncated cone, inverse truncated
cone, truncated pyramid, inverse truncated pyramid, cone, inverse
cone, pyramid, inverse pyramid, spherical shell, inverse spherical
shell. This means that the structures can be formed as elevations
or depressions in the semiconductor body. Within the manufacturing
tolerances, the structures are given or at least approximated by
the geometric bodies mentioned above. This means that, with regard
to manufacturing tolerances, the structures can deviate from the
perfect geometric shape. Furthermore, the structures can have any
base area. For example, it is possible for the structures being
formed as pyramids, inverse pyramids, truncated pyramids or inverse
truncated pyramids to have an n-angular base, where n is
.gtoreq.3.
[0050] A maximum lateral extension of the structure may be at least
400 nm. The maximum lateral extension is the maximum diameter of
the structures, for example, at their base. The maximum lateral
extension is preferably at least 400 nm for a large part of the
structures, i.e., for at least 50 percent, in particular for at
least 75 percent, of the structures. Such a maximum lateral
extension has proven to be advantageous to enlarge the contact area
between the semiconductor body and the first connection element
since such large structures make it possible to enlarge the contact
area particularly significantly.
[0051] The structuring may have a density of structures, wherein
the density of the structures increases towards a radiation exit
surface of the semiconductor laser diode.
[0052] In the region of the radiation exit surface, the
semiconductor laser diode has the area in which the temperature of
the semiconductor body becomes greatest during operation. To
counteract the effect of the thermal lens, it is advantageous to
apply as many structures of the structuring as possible in the
areas of high temperature and thus carry out the structuring there
in a particularly high density. In particular, the density of the
structuring can be chosen to follow a temperature profile of the
emitter region without structuring during operation of the
semiconductor laser. This means that the higher the temperature in
a semiconductor laser diode of the same construction without
structuring at a certain location in the emitter region, the higher
the density of the structures of the structuring is selected at
this location.
[0053] For example, the density can be adjusted by selecting the
distance between adjacent structures and selecting the size of the
structures.
[0054] The closer the structures are to the radiation exit surface,
the smaller the distance may be between the adjacent structures.
Keeping the same size of the structures, the density of the
structures can be adjusted by the distance between adjacent
structures. The closer the structures are to the radiation exit
surface, the smaller the distance is chosen so that the distance
between adjacent structures is chosen to be particularly small in
such areas where a semiconductor laser diode, which is the same
construction but is free of the structuring, has a particularly
high temperature. In this way, the density of the structures is
increased in these areas compared to other areas.
[0055] In the emitter region, the semiconductor body may comprise a
connection region that directly adjoins the first connection
element at the contact area, wherein the connection region is not
completely penetrated at any point. The connection region of the
semiconductor body, for example, is a particularly highly doped
layer of the semiconductor body. For example, the connection layer
is a highly p-doped layer. The dopant concentration can be at least
5*10{circumflex over ( )}18/cm{circumflex over ( )}3, especially at
least 10{circumflex over ( )}19/cm{circumflex over ( )}3. This
layer can also be referred to as the final or cap layer.
[0056] In the vertical direction, the connection region can project
beyond the areas of the semiconductor body that do not belong to
the emitter region. This means that the semiconductor body is
thicker in the connection region than in neighboring regions,
wherein the increased thickness is due to the semiconductor layer
in the connection region.
[0057] The structuring is located in the connection region, wherein
the structures are formed such that the connection region is not
completely pierced at any point. In other words, the structuring
partially reduces the thickness of the connection region. At no
point, however, does it comprise a hole extending through the
connection region. This ensures that the first connection element
in the emitter region can completely adjoin the connection region
of the semiconductor body and does not pierce the connection region
of the semiconductor body.
[0058] This ensures that the first connection element adjoins a
region of the semiconductor body having a particularly low ohmic
resistance due to its high doping.
[0059] The semiconductor body may comprise a subregion disposed
laterally adjacent to the emitter region. In particular, the
semiconductor body in the subregion has at least in places a
further structuring comprising further structures, wherein the
further structuring is configured to weaken secondary modes.
[0060] In the subregion, the semiconductor body is preferably not
electrically contacted by the first connection element. For
example, in the subregion, an electrically insulating insulation
element is located between the semiconductor body and the first
connection element and/or the first connection element is formed
only in the emitter region. The semiconductor laser diode can cover
many of the subregions. For example, if the semiconductor laser
diode comprises a single emitter region, the subregions can be
arranged on both sides of a longitudinal axis of the emitter region
so that in this instance the semiconductor laser diode comprises
two subregions. If the semiconductor laser diode comprises two or
more emitter regions, the subregions can be arranged in particular
between the emitter regions. The semiconductor body then consists,
for example, of subregions and emitter regions.
[0061] In the subregion, according to this example, the
semiconductor body exhibits a further structuring configured to
weaken the secondary modes, for example, by scattering
electromagnetic radiation and/or absorbing electromagnetic
radiation at the further structures of the further structuring. The
weakening can be so strong that oscillation of the secondary modes
is suppressed.
[0062] The further structuring can also contribute to improved heat
dissipation of the semiconductor body during operation of the
semiconductor laser diode.
[0063] An electrically insulating insulation element that
completely covers the semiconductor body in the subregion on its
side facing the first connection element may be arranged between
the subregion and the first connection element. The insulation
element is, for example, a layer or a sequence of layers formed
from electrically insulating material.
[0064] For example, the insulation element is a layer of silicon
dioxide or a layer of silicon nitride. Due to the electrical
insulation of the subregion by the insulation element, it is
possible to form the first connection element over a large area so
that it can cover the semiconductor body in the emitter region and
in the subregion. In this way it is possible that in extreme
instances the semiconductor body is completely covered by the first
connection element on its entire side facing the first connection
element. By using a first connection element having high thermal
conductivity, it is possible to dissipate heat from the
semiconductor body in a particularly effective manner during
operation of the semiconductor laser diode.
[0065] The structures of the structuring may have an average height
that is smaller than an average height of the further structures of
the further structuring. In other words, the structuring in the
emitter region may have lower structures than the further
structuring in the subregion. The height can be measured along the
vertical direction.
[0066] In the event that the connection region of the semiconductor
body also extends into the subregion, it is particularly possible
that the further structuring has further structures that completely
pierce the connection region. This is possible in the subregion
since an electrical connection of the semiconductor body is not
wanted there anyway.
[0067] In this way, the further structures having a greater height
protrude further into the semiconductor body resulting in an
improvement of their effect in reducing secondary modes.
[0068] The structures and/or the further structures may be produced
by etching. This means that the structuring and/or the further
structuring are produced by an etching process. The etching process
can be dry chemical or wet chemical etching, for example. For
example, the structures as well as the further structures can be
produced photolithographically by a stepper or so-called natural
lithography. The feature wherein the structures and/or the further
structures are produced by etching is in particular a physical
feature that can be verifiable at the finished product. For
example, conventional analysis methods in semiconductor technology
such as microscopic or electron microscopic tests can be used to
determine whether a structure has been produced by etching or by an
alternative manufacturing process. The etching is thus clearly
verifiable at the finished product.
[0069] In the following, the semiconductor laser diodes described
here will be explained in more detail using examples and the
corresponding figures.
[0070] Identical, equivalent or equivalently acting elements are
indicated with the same reference numerals in the figures. The
figures and the proportions of the elements depicted in the figures
shall not be considered to be true to scale unless units are
expressly indicated. Individual elements can rather be illustrated
exaggeratedly large for the purpose of better representability
and/or better clarification.
[0071] FIG. 1 shows a schematic view of a conventional
semiconductor laser diode. The semiconductor laser diode comprises
a carrier 1 to which the semiconductor body 2 is applied. The
semiconductor body 2 has a central emitter region 5 as well as two
subregions 6 surrounding and adjoining the emitter region 5 on both
sides. In the emitter region 5, the semiconductor laser diode has
its radiation exit surface 7.
[0072] A thermal camera is directed at the radiation exit surface 7
to investigate the temperature behavior. The graphic application in
FIG. 1 shows the temperature T depending on the position P on the
side surface of the semiconductor body 2 facing the thermal camera
for different operating currents with which the semiconductor laser
diode is operated. It can be seen that at the radiation exit
surface 7, the temperature in the emitter region 5 rises strongly
with increasing operating current. This results in formation of a
thermal lens as described, which reduces the efficiency and beam
quality of the laser radiation generated by the semiconductor laser
diode during operation.
[0073] In connection with the schematic sectional view of FIG. 2, a
first example of a semiconductor laser diode is explained in more
detail. The semiconductor laser diode comprises a carrier 1. The
carrier 1 can, for example, be a heat sink configured for the
active or passive cooling of a semiconductor body 2 of the
semiconductor laser diode.
[0074] The semiconductor body 2 of the semiconductor laser diode
comprises an n-conductive region 21, a p-conductive region 22 and
an active region 23 between the n-conductive region 21 and the
p-conductive region 22. During operation of the semiconductor laser
diode, electromagnetic radiation is generated and amplified in the
active region.
[0075] The semiconductor body is divided into a central emitter
region 5 surrounded on both sides by subregions 6. The
semiconductor body is electrically connected on the p-side only in
the emitter region 5. For this purpose, the semiconductor body
comprises a connection region 24 formed in the emitter region 5 and
which, for example, is formed with a highly p-doped semiconductor
material. In this example, the connection region 24 projects above
the remaining semiconductor body 2 along a strip in a vertical
direction V perpendicular to the lateral directions L running
parallel to the main extension plane of the semiconductor body.
[0076] The semiconductor laser diode also has a radiation exit
surface 7 located on an outer facet of the semiconductor body in
the region of the active region 23 within the emitter region 5.
[0077] The semiconductor body 2 is electrically conductively
connected on the p-side via the first connection element 3. The
first connection element 3, for example, is formed by a metal layer
produced by sputtering or evaporation. In the connection region 24,
the connection element 3 is in direct contact with the
semiconductor body 2. In the subregions 6, each respective
insulation element 8, formed for instance from an electrically
insulating material such as silicon nitride, is arranged between
the semiconductor body 2 and the first connection element 3.
[0078] In the emitter region 5 on its side facing the first
connection element 3, the semiconductor body 2 now has a
structuring 26 comprising a plurality of structures 26a. Compared
to a flat and plane version of the connection region 24, the
structuring 26 results in an enlargement of a contact area 28
between the semiconductor body 2 and the first connection element
3. The connection region 24 is not completely pierced by the first
connection element 3, as the structures 26a do not extend
throughout the connection region 24.
[0079] The connection element 3 can, for example, be thermally and
electrically connected to the carrier 1 by a solder material.
[0080] On the side facing away from the first connection element 3,
the semiconductor body 2 has a second connection element 4, via
which the semiconductor body is contacted on the n-side. The second
connection element 4 comprises for instance a contact point 41,
which can be a bond pad electrically connected to a contact wire
42.
[0081] Both the first connection element 3 and the second
connection element 4 completely cover the two main surfaces, i.e.,
the bottom surface and the top surface, of the semiconductor body
2. This enables a particularly good thermal bonding of the
semiconductor body 2 to the carrier 1. Due to the structuring 26,
the thermal bonding in the emitter region 5 is particularly good,
resulting in suppression of formation of the thermal lens.
[0082] In connection with FIG. 3, a further example of a
semiconductor laser diode described here is illustrated in more
detail in a schematic sectional view. In addition to the example in
FIG. 2, the semiconductor laser diode in FIG. 3 also has a further
structuring 27 of the semiconductor body 2 in the subregions 6. The
further structuring 27 comprises structures 27a. The further
structuring 27 extends deeper into the semiconductor body than the
structuring 26. The further structuring 27, however, does not cut
through the active layer 23.
[0083] On its side facing the first connection element 3, the
further structuring 27 is covered by the insulation 8 and in this
way, the subregions 6 are not electrically connected.
[0084] The schematic illustration of FIG. 4 shows a top view of an
example of my semiconductor laser diode. The semiconductor laser
diode comprises a central emitter region 5 extending in the form of
a bar and being surrounded on both sides by the subregions 6. The
schematic illustration of FIG. 4 shows regions of different
temperatures T1, T2, T3. The temperature T2 is greater than the
temperature T1, and the temperature T3 is greater than the
temperature T2.
[0085] Thus, FIG. 4 shows that the temperature is highest in the
region of the radiation exit surface 7 and thus the thermal lens
effect is most pronounced there. To counteract this, the higher the
temperature of a semiconductor laser diode is without the
structuring 26, the denser the structuring 26 can be formed in the
emitter region 5. This means that the smaller the distance is from
the radiation exit surface 7, the denser the structures 26a of the
structuring 26 can be arranged and the smaller their distance d
from each other is chosen. The temperature profile of the emitter
region 5 resembles a parabola, wherein the structuring 26 can be
controlled according to this shape.
[0086] In connection with the schematic representations of FIGS. 5A
to 5D, different examples of formation of the structuring 26 are
shown. The structures 27a of the further structuring 27 can be
formed in the same or a similar way.
[0087] FIGS. 5A and 5B show the forms of the structures 26a and 27a
as spherical shells, wherein in connection with FIG. 5B, the height
h of the structures is chosen to be larger. The structures 26a and
27a each have a distance d from each other. As an alternative to
the spherical shells, the structures can also be formed as inverse
spherical shells, which are arranged in the semiconductor body 2 as
depressions or recesses.
[0088] FIG. 5C shows a version of the structures 26a and 27a as
truncated cones or truncated pyramids. For example, if the
structures 26a and 27a are truncated cones having a diameter D of
400 nm and a height h of 160 nm as well as a cone angle .alpha. of
75 degrees, by arranging the structures 26 and 27 in a
two-dimensional hexagonal close packed manner, roughly a doubling
of the base area can be achieved since, in addition to the base
area of the truncated cone, its lateral surface also contributes to
the contact area 28.
[0089] In addition to the structures 26a and 27a shown in FIGS. 5A
to 5D, the inverse structures can also be used as depressions or
recesses in the semiconductor body.
[0090] In particular, the structures 26a as well as the further
structures 27a can be produced by etching. The etching can be
carried out with the help of a mask using a photolithographic
process and natural lithography.
[0091] Due to the structures 26a, in addition to an enlarged
contact area 28 for dissipating heat, there is also an enlarged
electrical contact area in the emitter region 5, which lowers the
electrical resistance for contacting. A further advantage of the
application of the structurings 26 and the further structurings 27
is that, without the need to change the general construction of the
semiconductor laser diodes, the structuring can be applied to
already existing component species of semiconductor laser diodes.
This means that the proposed procedures for reducing the thermal
lens can be applied to semiconductor laser diodes that have already
been produced so that they can be implemented particularly quickly
and cost-effectively.
[0092] The schematic top views in FIGS. 6A and 6B show excerpts of
an intermediate product of the examples of my semiconductor laser
diodes. In the figures, the emitter region 5 as well as a subregion
6 are shown in extracts. The structures 26a are located in the
emitter region 5 and the further structures 27a are located in the
subregion 6. According to the example shown in FIG. 6A, the
structural form as well as the structural sizes are the same.
According to the example in FIG. 6B, the further structures 27a are
selected to have a greater height h than the structures 26a. The
structures 27a are particularly suitable for weakening the
secondary modes, whereas the structures 26a are formed to be so
flat that they do not pierce the connection region 24 of the
semiconductor laser diode.
[0093] In the emitter region 5, the structurings 26a are
subsequently covered with a metallization, which is part of the
first connection element 3. In the subregion 6, the further
structures 27a are covered with an electrically insulating material
of the insulation element 8.
[0094] Overall, the semiconductor laser diodes are characterized by
particularly good heat dissipation in the emitter region 5 of the
semiconductor body 2, wherein the heat dissipation can be improved
especially in the region of the radiation exit surface 7, i.e., in
the region of the light exit facet. In this way, the effects of the
thermal lens are reduced, resulting in a semiconductor laser diode
having an improved beam quality and an increased efficiency in
generating laser radiation.
[0095] My laser diodes are not restricted to the examples by the
descriptions thereof made with reference to the examples. This
disclosure rather comprises any novel feature and any combination
of features, including in particular any combination of features in
the appended claims, even if the feature or combination is not
itself explicitly indicated in the claims or examples.
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