Semiconductor optoelectronic component with improved heat dissipation

Abstract

The invention relates to a semiconductor optoelectronic component comprising a semiconductor stack. This stack includes an active layer, two confinement layers located respectively on either side of the active layer, and two electrode layers, each at least partially covering one of the respective confinement layers. A first face of the stack comprises a waveguide formed by a ribbon delimited by two transverse walls, said waveguide comprising at least a portion of the confinement layer adjacent to said first face, referred to as the first confinement layer, and at least a portion of the electrode layer adjacent to said first face, referred to as the first electrode layer.The optoelectronic component further comprises a metallic layer covering at least part of the first face of the stack, said metallic layer coming into contact with the portion of the first electrode layer located in the waveguide; an insulating layer located between the metallic layer and the first face of the stack around the portion of the first electrode layer located in the waveguide, said insulating layer comprising, in particular, being formed by aluminum nitride.

Description

Title of the invention: Semiconductor optoelectronic component having improved heat dissipation

[0001] The invention relates to the field of semiconductor optoelectronic components.

[0002] Such optoelectronic components typically comprise a stack of layers of semiconductor materials, in particular formed by epitaxy, intended to emit light from an electric current.

[0003] Typically, the optoelectronic component comprises two electrical contacts for conveying the electric current into the stack of semiconductors. The electrical injection is carried out in an active zone at the origin of the emission of a light wave. For this purpose, one face of the stack comprises a waveguide formed of a ribbon delimited by two transverse walls. The waveguide can in particular be defined by two trenches. One of the electrical contacts is positioned on one face of the stack of semiconductors. The other electrical contact is located at the top of the waveguide, so as to localize the electric field, and thus create an active zone.

[0004] However, the electro-optical conversion is not complete. Part of the energy delivered by the injected current is not transformed into a light wave and is dissipated as heat by the Joule effect. In the best case, the conversion rate is between 60 and 65%, however it is generally lower. Thus, when the active zone emits light, the optoelectronic component generates heat which is not negligible. The increase in temperature can reduce the performance, reliability or durability of the component. The heat dissipation of such optoelectronic components is therefore a key problem.

[0005] It is known to integrate a heat sink on the semiconductor stack. However, such a solution may not be sufficient.

[0006] In particular, certain topologies of optoelectronic components are intrinsically disadvantaged for efficient heat dissipation. Optoelectronic component topologies are known which comprise insulating layers which make it possible to localize the electrical injection in the semiconductor stack. Such insulating layers are notably made of dielectric materials, such as for example silicon dioxide (SiO2), silicon nitride (Si3N4) or polymer materials such as benzocyclobutene. However, these materials have very low thermal conductivity values, for example of the order of 1.2 Wm 1 .K 1 for thin-film silicon dioxide, or 2.5 Wm *.K1 for silicon nitride. thin-film silicon, or 0.3 Wm *.K1 for benzocyclobutene.

[0007] A solution is therefore sought to improve the heat dissipation of a semiconductor optoelectronic component.

[0008] For this purpose, a semiconductor optoelectronic component is proposed comprising a stack of semiconductors, said stack comprising an active layer, two confinement layers located respectively on either side of the active layer, two electrode layers each covering at least in part a respective layer among the confinement layers, a first face of said stack comprising a waveguide formed of a ribbon delimited by two transverse walls, said waveguide comprising at least a portion of the confinement layer adjacent to said first face, called the first confinement layer, and at least a portion of the electrode layer adjacent to said first face, called the first electrode layer, said optoelectronic component further comprising: - a metal layer covering at least in part the first face of the stack,said metal layer coming into contact with the portion of the first electrode layer located in the waveguide, - an insulating layer located between the metal layer and the first face of the stack around the portion of the first electrode layer located in the waveguide, said insulating layer comprising, in particular being formed by, aluminum nitride.

[0009] Thanks to the aluminum nitride, the optoelectronic component according to the invention has improved heat dissipation compared to the prior art.

[0010] According to one embodiment, each of the transverse walls delimiting said waveguide forms a side wall of a respective trench formed in the first face of the stack, each trench extending from the first electrode layer into the first confinement layer.

[0011] According to one embodiment, a surface of said portion of the first electrode layer, included in the first face, has undulations.

[0012] According to a variant, the undulations are located in a surface of the first electrode layer which is in contact with the metal layer.

[0013] According to a variant, said undulations form, seen from above, a network of cavities.

[0014] According to a particular variant, said network of cavities comprises, seen from above, first rounded cavities having a first span and second rounded cavities having a second span, the first span being greater than the second span and said second cavities being between said first cavities.

[0015] According to one variant, the undulations have a height of between 500 and 900 nm.

[0016] According to one embodiment, the portion of the first electrode layer located in the waveguide has a minimum thickness of between 100 and 200 nm.

[0017] According to one embodiment, the semiconductor optoelectronic component comprises a heat sink, and an outer surface of the portion of the first electrode layer is fixed against the heat sink.

[0018] The invention further relates to a semiconductor optoelectronic component comprising a stack of semiconductors, said stack comprising an active layer, two confinement layers located respectively on either side of the active layer, two electrode layers each covering at least in part a respective layer among the confinement layers, a first face of said stack comprising a waveguide formed from a ribbon delimited by two transverse walls, said waveguide comprising at least a portion of the confinement layer adjacent to said first face, called the first confinement layer, and at least a portion of the electrode layer adjacent to said first face, called the first electrode layer, so as to allow, in the active layer, an active zone between the confinement layers for the formation of a light wave, semiconductor optoelectronic component, in which a surface of said portion of the first electrode layer, included in the first face, has undulations.

[0019] Thanks to the corrugations, the portion of the first electrode layer included in the waveguide has a larger external surface compared to the prior art, which makes it possible to increase the heat dissipation surface and improves the cooling of the optoelectronic component. These corrugations therefore form a structure of the semiconductor stack and are thus as close as possible to the active zone which generates heat. This allows faster heat treatment than in the prior art.

[0020] This optoelectronic component may comprise any of the characteristics described in relation to the preceding optoelectronic component.

[0021] Other characteristics and advantages of the present invention will appear better on reading the description which follows in relation to the following appended figures:

[0022] [Fig-1]: [Fig.l] illustrates a stack of semiconductors of an opto component electronics according to an example of the invention;

[0023] [Fig.2]: [Fig.2] illustrates an optoelectronic component according to an example of the invention comprising the stack shown in [Fig.l];

[0024] [Fig.3]: [Fig.3] illustrates a step of manufacturing the optoelectronic component according to an example of the invention represented in [Fig.2];

[0025] [Fig.4]: [Fig.4] illustrates a manufacturing step of the optoelectronic component according to an example of the invention represented in [Fig.2];

[0026] [Fig.5]: [Fig.5] illustrates a manufacturing step of the optoelectronic component according to an example of the invention represented in [Fig.2];

[0027] [Fig.6]: [Fig.6] illustrates an example of a cavity network used in the component optoelectronics according to an example of the invention shown in [Fig.2].

[0028] [Fig.l] illustrates a stack of semiconductors 100 of an optoelectronic component according to an example of the invention.

[0029] The stack 100 comprises an active layer 103 in which an electrical injection makes it possible to obtain an optical gain. Two confinement layers 104a, 104b are located respectively on either side of the active layer 103. In particular, a confinement layer 104a is located on one side of the active layer 103; another confinement layer 104b is located on the opposite side of the active layer 103. The confinement layers 104a, 104b have in particular refractive indices lower than that of the active layer 103, thus making it possible to confine the light wave in the active layer 103 and to guide it. Two electrode layers 106a, 106b each cover at least in part a respective layer among the confinement layers 104a, 104b.In particular, an electrode layer 106a covers a confinement layer 104a, in particular on a side opposite the active layer 103; another electrode layer 106b covers the other confinement layer 104b, in particular on a side opposite the active layer 103. In particular, the electrode layers 106a and confinement 104a located on one side of the active layer 103, and the electrode layers 106b and confinement 104b located on the other side of the active layer 103 have dopings of opposite types. For example, in [Fig.l], the electrode 106a and confinement 104a layers located above the active layer 103 have p-type doping, and the electrode 106b and confinement 104b layers located below the active layer 103 have n-type doping. But the reverse is also possible.In particular, in the confinement layers, 104a, 104b, the doping profile increases progressively from the active layer 103 towards each electrode layer 106a, 106b so as to maximize the radiative recombinations of the carriers and allow a transparency threshold near the active layer.

[0030] The active layer 103 may comprise a quantum well layer 101. In particular, two enlarged optical layers 102a, 102b are located respectively on either side of the quantum well layer 101. The quantum well layer 101 serves for the confinement and recombination of the electrical charges. The enlarged optical layers make it possible to confine the photons. The active layer 103 may comprise several quantum well layers 101 superimposed on one another.

[0031] [Fig.2] shows a partial view of an optoelectronic component 10 according to a example of the invention, comprising the semiconductor stack 100 illustrated in [Fig.l]. [Fig.2] corresponds to a sectional view of the stack 100 illustrated in [Fig.l], in a direction perpendicular to the plane of [Fig.l]. Only a first electrode layer 106a and a first confinement layer 104a located near a first face S of the stack 100 are shown.

[0032] The first face S of the stack 100 comprises a waveguide G. The waveguide G forms a ribbon defined by two transverse walls 107, 108. A portion 1006a of the first electrode layer 106a and a portion 1004a of the first confinement layer 104a are included in the waveguide G. In particular, the walls 107, 108 transversely intersect the first electrode layer 106a and the first confinement layer 104a. Thus, in particular, over a first height the waveguide G is formed by the portion 1006a of the first electrode layer 106a; and over a second height, the waveguide G is formed by the portion 1004a of the first confinement layer 104a. In particular, each transverse wall 107, 108 therefore transversely intersects the first electrode layer 106a over the first height, and the first confinement layer 104a over the second height.

[0033] The waveguide G makes it possible to define, in the active layer, an active zone between the confinement layers 104a, 104b. In a manner known per se, the active zone of the active layer forms a volume in which the light wave is produced. In particular, during operation of the optoelectronic component 10, the injection of the electric current is localized at the top of the waveguide G, making it possible to form the active zone below the waveguide G, and thus to achieve the gain necessary to obtain a laser.

[0034] A metal layer 116 is deposited on the first face S of the stack 100 to allow electrical injection into the stack from an electrical source. In particular, the metal layer 116 is in contact with the portion 1006a of the first electrode layer 106a, located in the waveguide G. Thus, the metal layer 116 can convey an electric current in the portion 1006a of the first electrode layer 106a.

[0035] An insulating layer 118 is located between the metal layer 116 and the first face S of the stack 100 around the portion 1006a of the first electrode layer 106 located in the waveguide G. This insulating layer 118 makes it possible to localize the injection of current in the portion 1006a of the first electrode layer 106a. The insulating layer 118 comprises, in particular is formed by, aluminum nitride (AIN). Aluminum nitride has, for example, a thermal conductivity of approximately 20 Wm *.K1 for a layer 10 nm thick, or a thermal conductivity of approximately 100 Wm '.K 1 for a layer 100 nm thick. Aluminum nitride is particularly advantageous, because it is an insulator which has a thermal conductivity superior to insulators used in prior art optoelectronic components, such as silicon dioxide (SiO2), silicon nitride (Si3N4) or polymer materials such as benzocyclobutene. Due to its proximity to the active area, the insulating layer 118 improves heat dissipation through the first face S. In addition, aluminum nitride is optically transparent over a wavelength range from ultraviolet down to 6 pm, which makes it particularly advantageous in optoelectronic components emitting in these wavelengths because it will not induce optical losses.

[0036] In particular, the contact between the metal layer 116 and the portion 1006a of the first electrode layer 106a, located in the waveguide G, is located on an extreme portion of the waveguide G located between the transverse walls 107, 108 so that when an electric field is applied, it is exerted vertically, in the stacking direction.

[0037] The stack 100 may comprise trenches 113, 114 in the first face S to define the waveguide G. By defining the waveguide G with trenches 113, 114, mechanical protection of the waveguide G is obtained by the remainder of the first face S. Alternatively, the waveguide G could be defined by etching the entire portion of the first face S surrounding the waveguide G, so as to obtain a completely planar surface around the waveguide G. In particular, each transverse wall 107, 108 of the waveguide G forms a side wall of a trench 113, 114. The trenches 113, 114 are formed in the first face S of the semiconductor stack 100, and extend from the surface of the first electrode layer 106a into the first confinement layer 104a.

[0038] The portion 1006a of the first electrode layer 106a included in the waveguide G has a first surface Se included in the first face S of the stack 100. Unlike the prior art, in the optoelectronic component 10, the first surface Se of the electrode layer 106a may have undulations W. These undulations W make it possible to increase the external surface of the first electrode layer 106a and, in doing so, the heat dissipation surface. This further improves the evacuation, by the first face S of the stack 100, of the heat emitted during the production of light waves by the active zone. Furthermore, the increase in the external surface of the first electrode layer 106a makes it possible to reduce the electrical contact resistance between the first electrode layer 106a and the metal layer 116 making electrical contact.

[0039] Seen from above, the corrugations W can form a network of cavities 110, 112, in particular a regular network of cavities, as for example schematically illustrated in [Fig.6]. By forming cavities on the surface, the corrugations W are easily obtained. The side walls of the cavities 110, 112 form surfaces of dis additional thermal sipation compared to a prior art in which the surface Se of the portion 1006a of the first electrode layer 106a, included in the waveguide G, is planar.

[0040] In the example illustrated in [Fig.6], the cavities 110, 112 have rounded shapes, in particular in the form of a circle. First cavities 110 have a span, in particular a diameter, which is greater than the span, in particular the diameter, of the second cavities 112. The second cavities 112 are located between the first cavities. Such a network of cavities makes it possible to efficiently distribute the undulations on the surface Se of the electrode layer 106a. The network of cavities forms in particular a regular network. The cavities 110, 112 could have shapes other than rounded.

[0041] To preserve the electrical functionality of the portion 1006a of the first electrode layer 106a located in the waveguide G, the portion 1006a has in particular a minimum thickness of 150 nm. In the waveguide G, the first electrode layer 106a, in particular the portion 1006a, has for example a thickness between the first confinement layer 1004a and the corrugations W, which is greater than or equal to a value between 100 and 200 nm. This minimum thickness guarantees that the first electrode layer 106a has sufficient electrical charges to ensure its electrode function. A thickness designates in particular a distance considered along the stacking direction.

[0042] Thus, compared to the prior art, the portion 1006a of the first electrode layer 106a, located in the waveguide G, notably comprises an excess thickness in which the undulations W are formed.

[0043] It is preferable that the corrugations W are not too high to allow filling of the concave surfaces of the corrugations W when forming an electrical contact on the portion 1006a. However, the heights of the corrugations W are preferably significant to obtain an improvement in heat dissipation compared to the prior art. Thus, for example, the corrugations have a height of between 500 and 900 nm. The height of a corrugation designates in particular the distance between two extreme points of the corrugation.

[0044] In particular, the metal layer 116 covers the corrugations W. Thus, the heat evacuated by the corrugations W can be directly transmitted by the metal layer 116.

[0045] In particular, the insulating layer 118 and the metal layer 116 extend in the trenches 113, 114. In particular, the insulating layer 118 and the metal layer 116 extend along the walls of the trenches 113, 114, leaving a free volume in the trenches 113, 114. In particular, the metal layer 116 extends along the walls of the corrugations W so as to leave a free volume in the hollows of the corrugations W. These free volumes facilitate the fixing of a heat sink on the first face S of the stack 100. In particular, during such fixing, the metal layer 116 and the insulating layer 118 are found between the first face S of the stack 100 and the heat sink. In particular, a solder used for fixing the heat sink can fill the free volumes, thus improving the fixing of the sink.

[0046] Figures 3 to 5 illustrate an example of a manufacturing process for the optoelectronic component illustrated in [Fig.2].

[0047] The stack of semiconductor layers 100, for example illustrated in [Fig. 3], is in particular formed by epitaxy, for example by molecular beam epitaxy or MOCVD. In [Fig. 3], only the first electrode layer 106a and the first confinement layer 104a are shown. Marking or lithography of the first face S of the stack 100 is then carried out, so as to define etching zones to form the laser guide G. Then the etching is carried out, after which the trenches 113, 114 are in particular formed, as illustrated for example in [Fig. 4]. The insulating layer 118 of aluminum nitride is then deposited on the first face S of the stack 100. Such deposition can be carried out by electrical or reactive sputtering, by an atomic layer deposition or ALD (for “Atomic Layer Deposition” in English) or fast ALD (for fast ALD). In [Fig.5], the corrugations W are formed by lithography and etching steps of the insulator layer 118 and the first electrode layer 106a. Then, the metal layer 116 is deposited to obtain the optoelectronic component illustrated in [Fig.2], .

[0048] The optoelectronic component 10 may be, for example, a semiconductor laser, such as a quantum cascade laser, or a light-emitting diode, in particular a laser diode. The optoelectronic component 10 may address spectral domains in the near to mid-infrared range, depending on the semiconductor materials used. The optoelectronic component is particularly advantageous in applications where thermal management is particularly restrictive.

Claims

Claims

1. Semiconductor optoelectronic component (10) comprising a stack of semiconductors (100), said stack (100) comprising an active layer (103), two confinement layers (104a, 104b) located respectively on either side of the active layer (103), two electrode layers (106a, 106b) each covering at least in part a respective layer among the confinement layers, a first face (S) of said stack (100) comprising a waveguide (G) formed of a ribbon delimited by two transverse walls (107, 108), said waveguide (G) comprising at least one portion (1004a) of the confinement layer (104a) adjacent to said first face (S), called first confinement layer, and at least one portion (1006a) of the electrode layer (106a) adjacent to said first face (S), called the first electrode layer,said optoelectronic component (10) further comprising: - a metal layer (116) at least partially covering the first face (S) of the stack (100), said metal layer (116) coming into contact with the portion (1006a) of the first electrode layer (106a) located in the waveguide (G), - an insulating layer (118) located between the metal layer (116) and the first face (S) of the stack (100) around the portion (1006a) of the first electrode layer (106a) located in the waveguide (G), said insulating layer (118) comprising, in particular being formed by, aluminum nitride.,

2. Semiconductor optoelectronic component (10) according to claim 1, wherein each of the transverse walls (107,108) delimiting said waveguide (G) forms a side wall of a respective trench (113,114) formed in the first face (S) of the stack (100), each trench (107,108) extending from the first electrode layer (106a) into the first confinement layer (104a).

3. Semiconductor optoelectronic component (10) according to claim dication 1 or 2, wherein a surface (Se) of said portion (1006a) of the first electrode layer (106a), included in the first face (S), has undulations (W).

4. The semiconductor optoelectronic component (10) according to claim 3, wherein the undulations (W) are located in a surface of the first electrode layer (106a) which is in contact with the metal layer (116).

5. Semiconductor optoelectronic component (10) according to claim 3 or 4, wherein said undulations (W) form, seen from above, an array of cavities (110, 112).

6. A semiconductor optoelectronic component (10) according to the preceding claim, wherein said array of cavities comprises, viewed from above, first rounded cavities (110) having a first span and second rounded cavities (112) having a second span, the first span being greater than the second span and said second cavities (112) being between said first cavities (110).

7. Semiconductor optoelectronic component (10) according to one of claims 3 to 6, in which the undulations (W) have a height of between 500 and 900 nm.

8. Semiconductor optoelectronic component (10) according to one of the preceding claims, wherein the portion (1006a) of the first electrode layer (106a) located in the waveguide (G) has a minimum thickness of between 100 and 200 nm.

9. A semiconductor optoelectronic component (10) according to one of the preceding claims, comprising a heat sink and wherein an outer surface of the portion (1006a) of the first electrode layer (106a) is fixed against the heat sink.

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