DE102016122676A1 - Semiconductor laser - Google Patents

Abstract

A semiconductor laser (1) with a semiconductor body (2), which has a semiconductor layer sequence (200) with an active layer (20) provided for generating radiation, is specified, wherein the active layer has a plurality of emission regions (3) in the lateral direction. and a perturbation region (4) is arranged within the semiconductor body between adjacent emission regions. A process for producing a semiconductor laser is also provided.

Description

The present application relates to a semiconductor laser.

Semiconductor lasers are known in which individual emitters are arranged laterally next to one another. These emitters are spatially separated from each other by V-shaped trenches and typically have a pitch of 30 μm. In an optical image of the total radiation emitted by the emitters, these V-shaped trenches lead to dark spots. For the generation of a spatially large and homogeneous emission width such lasers are therefore only partially suitable.

One object is to specify a semiconductor laser with which the homogeneity of the emitted laser radiation in the lateral direction is improved. Furthermore, a method is to be specified, with which a semiconductor laser with a high homogeneity of the radiated radiation intensity can be produced easily and reliably.

These objects are achieved by a semiconductor laser or a method according to the independent patent claims. Further embodiments and expediencies are the subject of the dependent claims.

A semiconductor laser with a semiconductor body is specified. The semiconductor laser is formed, for example, as an edge-emitting semiconductor laser.

In accordance with at least one embodiment of the semiconductor laser, the semiconductor body has a semiconductor layer sequence with an active layer provided for generating radiation. The active layer is provided for example for generating radiation in the ultraviolet, visible or infrared spectral range. For example, the active layer has a quantum structure, such as a multi quantum well (MQW). For example, the active layer is disposed between a first semiconductor layer of a first conductivity type and a second semiconductor layer of a second conductivity type different from the first conductivity type such that the active layer is in a pn junction.

The semiconductor body can also have more than one active layer, for example two or more active layers, which are arranged one above the other in the vertical direction. For example, adjacent active layers in the vertical direction are electrically conductively connected to one another by means of a tunnel junction. In other words, the active layers stacked one above the other in the vertical direction may be electrically connected to each other in series.

The semiconductor body has, for example, one, in particular exactly one, web-shaped region. The ridge-shaped portion is provided for waveguiding along a main radiation direction of the semiconductor laser.

In accordance with at least one embodiment of the semiconductor laser, the active layer has a plurality of emission regions in the lateral direction. For example, at least two emission regions, in particular all emission regions arranged side by side in the lateral direction, can be externally electrically contacted independently of one another during operation of the semiconductor laser.

In case of doubt, a lateral direction runs parallel to a main extension plane of the semiconductor layers of the semiconductor layer sequence and perpendicular to the main emission direction of the semiconductor laser.

A vertical direction is in doubt perpendicular to the main extension plane of the semiconductor layers of the semiconductor layer sequence.

A lateral extent of an emission range has, for example, between 10 μm and 500 μm inclusive, for example between 20 μm and 300 μm inclusive.

In accordance with at least one embodiment of the semiconductor laser, the semiconductor laser has an interference region.

By way of example, the interference region is arranged within the semiconductor body. The interference region is thus part of the semiconductor body.

For example, the interference region between adjacent emission regions is arranged, in particular seen along the vertical direction on the semiconductor laser, ie in a plan view of the semiconductor laser.

The interference region is provided in particular for the purpose of ensuring that radiation propagating in the semiconductor laser during operation of the semiconductor laser, in particular radiation having a peak wavelength of the radiation to be generated, does not appear to be amplified in the region of the interference region. Rather, this radiation is absorbed selectively. In other words, contrary to the usual tendency of lossless radiation propagation within a waveguide, the noise region is deliberately designed to achieve radiation absorption.

In a plan view of the semiconductor laser, the interference region extends in particular parallel to a main emission direction of the semiconductor laser. The interference region is in particular provided for suppressing or at least weakening radiation components propagating transversely to the main emission direction, in order to suppress oscillation of laser modes in the lateral direction, ie perpendicular to the main emission direction.

In at least one embodiment of the semiconductor laser, the semiconductor laser has a semiconductor body which has a semiconductor layer sequence with an active layer provided for generating radiation. The active layer has a plurality of emission regions in the lateral direction. Within the semiconductor body, an interference region is arranged between adjacent emission regions.

According to at least one embodiment of the semiconductor laser, the interference region in an operation of the semiconductor laser, in which the emission regions emit coherent radiation, acts to absorb the radiation propagating in the semiconductor body. In particular, radiation components which propagate perpendicular to the main emission direction in the lateral direction are suppressed or at least attenuated by means of the interference region.

According to at least one embodiment of the semiconductor laser, the interference region is arranged in the active layer or the interference region is spaced in the vertical direction by at most 3 μm from the active layer. In a semiconductor laser having a plurality of active layers, the maximum distance in the vertical direction refers to the distance to the active layer closest to the noise region.

In contrast to a conventional laser structure, an interference region is thus located in places within the active layer or in the vertical direction, at least in the vicinity of the active layer, which has a targeted absorbing effect on the radiation to be generated in the active layer.

In accordance with at least one embodiment of the semiconductor laser, the interference region is a doping region in which a doping is different from a doping of a laterally adjoining material. For example, a concentration for at least one dopant in the noise region differs by at least 20%, or at least 50%, from the concentration of this dopant in a laterally adjacent material.

For example, the impurity region to a dopant concentration between 10 ¹⁸ cm ^-3 and 10 ²³ cm ^-3 inclusive.

The higher the doping concentration, the stronger the radiation absorption in the noise region can be. For example, free carrier absorption can cause radiation absorption.

In accordance with at least one embodiment of the semiconductor laser, the active layer extends continuously over at least two adjacent emission regions, wherein the active layer acts amplifying during operation of the semiconductor body only in the emission regions for the radiation to be generated. In particular, the semiconductor body is free of recesses, which cuts through the active layer between adjacent emission regions. In other words, the noise region is a region of the semiconductor body in which the material of the active layer is not removed between the adjacent emission regions. For example, the active layer and / or a layer arranged above or below the active layer is locally modified, for example by local introduction of dopants.

According to at least one embodiment of the semiconductor laser, a distance between adjacent emission regions is between 0.5 μm and 25 μm inclusive. The smaller the distance between adjacent emission regions, the lower the risk that, in the case of optical imaging, the dark regions which arise between the emission regions of the total radiation emitted by the semiconductor laser have a disturbing effect. On the other hand, efficient radiation absorption can be achieved in a simplified manner with a larger lateral extent. It has been found that a laterally homogeneous radiation and an efficient radiation absorption for the suppression of lateral modes can be reliably achieved by a distance in said region.

In accordance with at least one embodiment of the semiconductor laser, the semiconductor body is arranged on a substrate.

For example, the substrate is a growth substrate for the epitaxial semiconductor layer sequence of the semiconductor body. Alternatively, the substrate may also be different from the growth substrate.

On a side facing away from the substrate, the web-shaped region of the semiconductor body has an upper side. The top is in particular free of indentations. In particular, the web-shaped region on the upper side has no recesses which extend into the active layer between two adjacent emission regions.

In accordance with at least one embodiment of the semiconductor laser, a contact layer is arranged on the semiconductor body. The contact layer is, for example, a metal layer deposited on the semiconductor body.

In accordance with at least one embodiment of the semiconductor laser, the contact layer is subdivided into a plurality of segments. The segments of the contact layer are in particular provided for independently controlling the emission regions during operation of the semiconductor laser. In particular, each emission area can be assigned exactly one segment, so that each emission area can be controlled individually.

In accordance with at least one embodiment of the semiconductor laser, the contact layer extends continuously over at least two emission regions, in particular over all emission regions.

A contact layer that extends continuously in the lateral direction is particularly suitable for a semiconductor laser in which a long spatial emission width is desired without individual emission regions having to be electrically actuated independently of each other.

In accordance with at least one embodiment of a method for producing a semiconductor laser, a semiconductor layer sequence with an active layer provided for generating radiation is provided. Within the semiconductor layer sequence, at least one interference region is formed.

In accordance with at least one embodiment of the method, a contact layer is applied to an upper side of the semiconductor layer sequence. The contact layer is used in particular for external electrical contacting of the semiconductor layer sequence.

In one embodiment variant, the contact layer is applied after the formation of the at least one interference region.

The formation of the at least one interference region and the application of the contact layer can therefore take place independently of one another. In particular, the contact layer can also cover at least one interference region in plan view of the semiconductor laser.

In an alternative embodiment variant, the contact layer is applied before the formation of the at least one interference region. In this case, the contact layer can serve as a mask for the formation of the at least one interference region. The formation of the contact layer and the interference region is thus self-aligned to each other. On a mask layer in addition to the contact layer can be omitted. Alternatively, however, a mask layer can be used which, for example, covers areas which are not covered by the contact layer and should not be formed as interference regions.

In accordance with at least one embodiment of the method, the at least one interference region is formed by means of an implantation method. For example, p-dopants such as carbon, beryllium, zinc or magnesium may be implanted. It has been shown that p-dopants represent particularly efficient loss mechanisms and are therefore particularly suitable for the interference region. Alternatively, it is also possible to use n-dopants, for example silicon or tellurium.

The method described is particularly suitable for the production of a semiconductor laser described above. Therefore, features described in connection with the semiconductor laser can also be used for the method and vice versa.

Further embodiments and expediencies will become apparent from the following description of the embodiments in conjunction with the figures.

• Die 1A und 1B ein Ausführungsbeispiel für einen Halbleiterlaser in Draufsicht (1B) und zugehöriger Schnittansicht (1A);
• die 2, 3 und 4 jeweils ein Ausführungsbeispiel für einen Halbleiterlaser; und
• die 5A bis 5C und 6A bis 6C jeweils ein Ausführungsbeispiel für ein Verfahren zur Herstellung eines Halbleiterlasers anhand von jeweils schematisch in Schnittansicht dargestellten Zwischenschritten.

Show it:

• The 1A and 1B an exemplary embodiment of a semiconductor laser in plan view ( 1B ) and associated sectional view ( 1A );
• the 2 . 3 and 4 in each case an exemplary embodiment of a semiconductor laser; and
• the 5A to 5C and 6A to 6C in each case one exemplary embodiment of a method for producing a semiconductor laser on the basis of intermediate steps respectively shown schematically in a sectional view.

The same, similar or equivalent elements are provided in the figures with the same reference numerals.

The figures are each schematic representations and therefore not necessarily to scale. Rather, comparatively small elements and in particular layer thicknesses may be exaggerated for clarity.

In the 1A and 1B an embodiment for a semiconductor laser is shown. The semiconductor laser 1 has a semiconductor body 2 with a semiconductor layer sequence 200 on. The epitaxially deposited semiconductor layer sequence, for example, forms the semiconductor body.

The semiconductor layer sequence 200 in particular has an active layer 20 on, between a first semiconductor layer 21 and a second semiconductor layer 22 is arranged. For example, the first semiconductor layer is n-type and the second semiconductor layer is p-type or vice versa.

The semiconductor laser 1 is formed as an edge-emitting semiconductor laser, along a main emission direction 9 emits coherent radiation during operation of the semiconductor laser. The main emission direction runs parallel to a main extension plane of the semiconductor layers of the semiconductor layer sequence 200 ,

The semiconductor laser 1 has a plurality of emission regions 3 on, which are arranged side by side in a lateral direction. The number of emission ranges can be selected within wide limits. For example, the semiconductor laser 1 between 2 and 100 inclusive, for example between 2 and 10 inclusive emission ranges 3 on.

Between two adjacent emission areas 3 is each a Störbereich 4 educated. The Störbereich 4 is parallel or at least substantially parallel to the main emission direction 9 , In a plan view of the semiconductor body 2 are adjacent emission areas 3 each by a Störbereich 4 separated from each other.

The active layer 20 extends in the lateral direction throughout at least two emission regions 3 , in particular over all emission regions of the semiconductor laser. The Störbereiche 4 are inside the semiconductor body 2 arranged.

The semiconductor body 2 is on a substrate 5 , For example, a growth substrate for the semiconductor layer sequence 200 arranged the semiconductor laser.

The active layer 20 acts in the emission regions in the operation of the semiconductor body amplifying the radiation to be generated. In contrast to this, the interference areas act 4 not amplifying for the radiation, but absorbing for the radiation propagating in the semiconductor body. In plan view of the semiconductor laser, this therefore has between adjacent emission regions 3 Interference areas for radiation absorption. An oscillation of laser modes perpendicular to the main emission direction 9 in the semiconductor body, is by means of the interference regions 4 efficiently suppressed. Recesses in the semiconductor body, which separate adjacent emission areas from each other, are not required for this purpose.

A lateral extension of the interference regions 4 perpendicular to the main emission direction is preferably between 0.5 and 25 microns including, for example, between 2 microns inclusive and including 20 microns.

The greater the lateral extent of the interference region, the stronger the radiation absorption within the interference region can be at the same doping concentration.

On the other hand, the distance between adjacent emission areas 3 the smaller, the smaller the lateral extent of the interference regions. Disturbing dark areas between two adjacent emission areas, in particular in the case of optical imaging of the total radiated radiation, are thereby avoided or at least attenuated. In particular, as compared with a conventional semiconductor laser in which adjacent emission regions are separated from each other by V-shaped trenches, comparatively smaller distances between adjacent emission regions can be obtained. A lateral extent of the interference regions in the areas mentioned has proven to be particularly suitable.

In the vertical direction, ie perpendicular to the main extension plane of the semiconductor layers of the semiconductor layer sequence 200 , the interference regions can completely through the semiconductor body 2 extend. In particular, the Störbereiche 4 in the active layer 20 arranged. A large spatial overlap with possible oscillating laser modes and efficient suppression of such modes is thus reliably achievable.

Deviating from the disturbance areas 4 however, extend only partially through the semiconductor body. For example, the first semiconductor layer 21 or the second semiconductor layer 21 or the active layer 20 be free from a disturbance area. In particular, two of the layers mentioned can also be free of an interference region.

The Störbereiche 4 may each be formed as a doping region in which a doping is different from a doping of a laterally adjacent material.

On top of the semiconductor body 2 is a contact layer 6 arranged, the electrical contacting of the second semiconductor layer 22 serves. The contact layer 6 is in a plurality of segments 61 divided, each segment 61 for the energization of an emission area 3 is provided. The individual emission regions can therefore be controlled independently of one another during operation of the semiconductor laser.

Furthermore, the semiconductor laser 1 on the semiconductor body 2 opposite side of the substrate 5 a mating contact layer 65 on. By applying an external electrical voltage between the contact layer 6 and the counter contact layer 65 may charge carriers from opposite sides into the active layer 20 be injected and recombine there under emission of radiation, in particular coherent radiation. However, the geometric arrangement of the contacts can be varied within wide limits.

The semiconductor body 2 has a web-shaped area 25 in which the emission areas 3 are arranged. An oscillation of modes between side surfaces 250 the web-shaped area, that is perpendicular to the main emission direction 9 , is determined by means of the interference regions 4 efficiently suppressed.

A lateral extent of the individual emission areas 3 is, for example, between 20 μm inclusive and 300 μm inclusive. The entire lateral extent of the semiconductor body 2 is for example between 0.5 mm and 5 cm.

A the substrate 5 opposite top 29 of the web-shaped area 25 of the semiconductor body 2 is free of indentations, in particular free of recesses that the active layer 20 in completely separate emission areas 3 divided. For the production of the interference areas 4 Thus, no production step is required in which a material removal of the semiconductor body, for example by etching, takes place.

The active layer 20 , the first semiconductor layer 21 and the second semiconductor layer 22 are typically each formed multi-layered. For example, the first semiconductor layer 21 and the second semiconductor layer 22 one waveguide layer and one on the active layer 20 Having the opposite side of the waveguide layer disposed cladding layer. The active layer 20 has, for example, a quantum structure, such as a quantum structure with a plurality of quantum wells and arranged between the quantum wells barrier layers. This is not explicitly shown in the figures for the sake of simplicity.

The semiconductor body 2 , in particular the active layer 20 Advantageously, a compound semiconductor material, for example, a III-V compound semiconductor material on.

III-V compound semiconductor materials are capable of generating radiation in the ultraviolet (Al _x In _y Ga _1-xy N) over the visible (Al _x In _y Ga _1-xy N, especially for blue to green radiation, or Al _x In _y Ga _1-xy P, in particular for yellow to red radiation) up to the infrared (Al _x In _y Ga _1-xy As) spectral range is particularly suitable. In each case, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1 and x + y ≦ 1, in particular with x ≠ 1, y ≠ 1, x ≠ 0 and / or y ≠ 0. With III-V compound semiconductor materials, In particular, from the said material systems, high internal quantum efficiencies can continue to be achieved in the generation of radiation.

Alternatively, an II-VI compound semiconductor material may find application.

This in 2 illustrated embodiment of a semiconductor laser 1 is essentially the same as in the context of 1A and 1B described embodiment.

In contrast to this, the semiconductor body 2 a plurality of vertically stacked active layers 20 on. The active layers are each between a first semiconductor layer 21 a first conductivity type and a second semiconductor layer 22 a second conductivity type arranged. The active layers 20 are by means of a tunnel junction 28 electrically interconnected in series. In the exemplary embodiment shown, the interference region extends continuously from the one active layer 20 to the other active layer 20 , Deviating from this, however, is also conceivable that the Störbereich 4 in the vertical direction only in places between the active layers 20 or completely outside one or all active layers 20 is trained.

Such active layers arranged one above the other in the vertical direction can also be used in the embodiments described in connection with the further figures.

This in 3 illustrated embodiment substantially corresponds to that in connection with the 1A and 1B described embodiment. In contrast to this are the interference regions 4 in the vertical direction outside the active layer 20 arranged. The risk of damage to the active layer 20 in the formation of the Störbereiche 4 is so reduced. The Störbereiche 4 are merely exemplary in the first semiconductor layer 21 arranged. Deviating from the Störbereiche can also in the second semiconductor layer 22 or both in the first semiconductor layer 21 as well as in the second semiconductor layer 22 be educated. A distance between the noise area and the nearest active layer 20 is preferably at most 3 microns, for example at most 2 microns. The smaller the distance to the active layer 20 is, the greater is typically the interaction with the radiation propagating in the semiconductor body.

This in 4 illustrated embodiment substantially corresponds to that in connection with the 1A and 1B described embodiment. In contrast to this is the contact layer 6 formed contiguous and extends throughout at least two adjacent emission areas 3 , in particular over all emission regions of the semiconductor laser. The formation of a lateral structuring of the contact layer is therefore not required. Despite a continuous in the lateral direction electrical contacting of the second semiconductor layer 22 can by means of the interference areas 4 can be achieved that the spread of unwanted laser modes between the side surfaces 250 of the web-shaped area 25 is suppressed.

Such a continuous contact layer 6 is particularly useful when the individual control of the emission regions during operation of the semiconductor laser is not required.

Such a continuous contact layer is also suitable for the other embodiments.

An exemplary embodiment of a method for producing a semiconductor laser is shown in FIGS 5A to 5C shown. In the figures, for the sake of simplicity, only the production of a single semiconductor laser is shown. In the production, however, a plurality of semiconductor lasers can be formed simultaneously on a substrate, wherein the individual semiconductor lasers are formed by singulation of the substrate.

As in 5A is shown, a semiconductor layer sequence 200 with an active layer 20 provided, for example on a substrate 5 , such as the growth substrate for the semiconductor layer sequence.

In the semiconductor layer sequence 200 will, as in 5B shown, a plurality of interference regions 4 educated.

The interference regions can be formed, for example, by means of an implantation method, wherein the penetration depth into the semiconductor body can be adjusted via the energy of the introduced dopants and, in particular, can also be varied during the introduction. The introduction of the dopants is indicated by the arrows 95 illustrated.

For a laterally defined introduction of the dopants, a mask 7 Find application, so that the interference areas 4 only in openings 70 the mask are formed. At the time of forming the noise regions, the semiconductor layer sequence 200 already in bar-shaped areas 25 structured or still unstructured. After the formation of the interference regions, the semiconductor material in the interference regions has a higher concentration of the introduced dopant than the laterally adjacent material of the same semiconductor layer, for example a concentration which is at least 30% higher. The concentration may also be at least two times or at least ten times higher.

After forming the noise regions 4 is on a the substrate 5 opposite top 29 of the semiconductor body 2 a contact layer 6 applied. The contact layer may be in the form of individual segments 61 or be formed continuously over several adjacent emission areas.

Other manufacturing steps such as the formation of a mating contact layer are not shown for ease of illustration.

That in the 6A to 6C described embodiment of a method substantially corresponds to that in connection with the 5A to 5C described embodiment. In contrast, the contact layer becomes 6 applied before the formation of the interference areas 4 he follows. The contact layer 6 can serve as a mask for the formation of the interference regions, so that the formation of the interference regions and the arrangement of the individual segments 61 the contact layer is done in self-aligned form. The contact layer 6 can in particular all areas of the semiconductor layer sequence 200 cover in which no Störbereiche are to be formed. For example, the contact layer 6 also over the side surface 250 of the web-shaped area 25 be guided, for example by means of a between the side surface and the contact layer 6 arranged insulation layer. Alternatively or additionally, a mask layer may be added to the contact layer 6 Application, the uncovered areas of the contact layer, which are not to be formed as interference regions covering.

The invention is not limited by the description with reference to the embodiments. Rather, the invention encompasses any novel feature as well as any combination of features, which in particular includes any combination of features in the patent claims, even if this feature or combination itself is not explicitly stated in the patent claims or the exemplary embodiments.

LIST OF REFERENCE NUMBERS

1

Semiconductor laser

2

Semiconductor body

200

Semiconductor layer sequence

20

active layer

21

first semiconductor layer

22

second semiconductor layer

25

rib-shaped area

250

side surface

28

Tunnel junction

29

top

3

emission region

4

interference area

5

substratum

6

contact layer

61

segment

65

Against contact layer

7

mask

70

opening

9

Main emission direction

95

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Claims (15)

Semiconductor laser (1) having a semiconductor body (2), which has a semiconductor layer sequence (200) with an active layer (20) provided for generating radiation, wherein the active layer has a plurality of emission regions (3) in the lateral direction and within the semiconductor body an interference region (4) is arranged between adjacent emission regions. Semiconductor laser after Claim 1 In an operation of the semiconductor laser in which the emission regions emit coherent radiation, the interference region for the radiation propagating in the semiconductor body has an absorbing effect. Semiconductor laser after Claim 1 or 2 , wherein the interference region is arranged in the active layer or spaced in the vertical direction by at most 3 microns from the active layer. Semiconductor laser according to one of the preceding claims, wherein the interference region is a doping region in which a doping of a doping of a laterally adjacent material is different. Semiconductor laser according to one of the preceding claims, wherein the active layer extends continuously over at least two adjacent emission regions and the active layer acts in operation of the semiconductor body only in the emission regions for the radiation to be generated amplifying. Semiconductor laser according to one of the preceding claims, wherein a distance between adjacent emission regions is between 0.5 μm and 25 μm inclusive. Semiconductor laser according to one of the preceding claims, wherein the semiconductor body is arranged on a substrate and has a web-shaped region (25), wherein an upper side facing away from the substrate (29) of the web-shaped region semiconductor body is free of indentations. Semiconductor laser according to one of the preceding claims, wherein on the semiconductor body, a contact layer (6) is arranged, which is divided into a plurality of segments (61). Semiconductor laser according to one of Claims 1 to 7 , wherein on the semiconductor body, a contact layer (6) is arranged, which extends continuously over at least two emission regions. Method for producing a semiconductor laser with the steps: a) providing a semiconductor layer sequence (200) with an active layer (20) provided for generating radiation; and b) forming at least one interference region (4) within the semiconductor layer sequence. Method according to Claim 10 in which a contact layer (6) is applied to an upper side (29) of the semiconductor layer sequence. Method according to Claim 10 or 11 in which the contact layer is applied after step b). Method according to Claim 10 or 11 in which the contact layer is applied before step b) and the contact layer serves as a mask for the formation of the at least one interference region. Method according to one of Claims 10 to 13 in which the at least one interference region is formed by means of an implantation process. Method according to one of Claims 10 to 14 in which a semiconductor laser according to one of Claims 1 to 9 will be produced.

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