阅读说明：本技术 边发射大功率激光器及其制造方法 (Edge-emitting high-power laser and manufacturing method thereof ) 是由 柯毛龙 李春勇 舒凯 仇伯仓 徐化勇 冯欧 于 2020-08-31 设计创作，主要内容包括：一种边发射大功率激光器及其制造方法,该边发射大功率激光器包括：N型衬底；N型缓冲层,设于所述N型衬底上；N型覆盖层,设于所述N型缓冲层上；下波导层,设于所述N型覆盖层上,所述下波导层无掺杂；有源区,设于所述下波导层上,所述有源区无掺杂；上波导层,设于所述有源区上,所述上波导层无掺杂；P型覆盖层,设于所述上波导层上,所述P型覆盖层的两端面分别设置有一绝缘层,所述绝缘层用于限制载流子在波导的端面的注入；P型欧姆接触层,设于所述P型覆盖层上,所述P型覆盖层和所述P型欧姆接触层通过蚀刻形成脊形的脊波导。本发明中的边发射大功率激光器可避免激光器腔面受热烧毁,提高了激光器的功率和可靠性。(An edge-emitting high power laser and a method of manufacturing the same, the edge-emitting high power laser comprising: an N-type substrate; the N-type buffer layer is arranged on the N-type substrate; the N-type covering layer is arranged on the N-type buffer layer; the lower waveguide layer is arranged on the N-type covering layer and is undoped; the active region is arranged on the lower waveguide layer and is undoped; the upper waveguide layer is arranged on the active region and is undoped; the P-type covering layer is arranged on the upper waveguide layer, two end faces of the P-type covering layer are respectively provided with an insulating layer, and the insulating layers are used for limiting the injection of current carriers into the end faces of the waveguides; and the P-type ohmic contact layer is arranged on the P-type covering layer, and the P-type covering layer and the P-type ohmic contact layer form a ridge waveguide in a ridge shape through etching. The edge-emitting high-power laser can avoid the cavity surface of the laser from being burnt by heating, and improves the power and the reliability of the laser.)

1. An edge-emitting high power laser, comprising:

an N-type substrate;

the N-type buffer layer is arranged on the N-type substrate;

the N-type covering layer is arranged on the N-type buffer layer;

the lower waveguide layer is arranged on the N-type covering layer and is undoped;

the active region is arranged on the lower waveguide layer and is undoped;

the upper waveguide layer is arranged on the active region and is undoped;

the P-type covering layer is arranged on the upper waveguide layer, two end faces of the P-type covering layer are respectively provided with an insulating layer, the insulating layers are used for limiting the injection of current carriers into the end faces of the waveguide, the P-type covering layer contains a high-aluminum component layer, and the high-aluminum component layer is oxidized to form the insulating layers at two ends of the P-type covering layer;

the P-type ohmic contact layer is arranged on the P-type covering layer;

and the P-type covering layer and the P-type ohmic contact layer form a ridge waveguide in a ridge shape through etching.

2. The edge-emitting high power laser of claim 1, wherein the ridge waveguide is etched to a lower portion of the P-type cladding layer.

3. The edge-emitting high power laser as claimed in claim 1, wherein the high aluminum component layer is made of AlGaAs or InGaAlAs material.

4. The edge-emitting high power laser as claimed in claim 1, wherein said upper waveguide layer and said lower waveguide layer have a higher forbidden bandwidth than said active region.

5. The edge-emitting high power laser as claimed in claim 1, wherein the material of said upper waveguide layer and said lower waveguide layer has a lower refractive index than said active region.

6. The edge-emitting high power laser as claimed in claim 1, wherein the thickness of the insulating layer is 50 to 200 nm.

7. The edge-emitting high power laser as claimed in claim 1, wherein the insulating layer has an extension length of 20-200 um in the P-type cladding layer.

8. The method of manufacturing an edge-emitting high power laser as claimed in any one of claims 1 to 7, comprising:

photoetching and positioning a ridge waveguide on an edge-emitting high-power laser main body, and etching the ridge waveguide, wherein the edge-emitting high-power laser main body comprises the N-type substrate, the N-type buffer layer, the N-type covering layer, the lower waveguide layer, the active region, the upper waveguide layer, the P-type covering layer and the P-type ohmic contact layer;

coating a dielectric layer;

corroding the end surface part of the ridge waveguide by adopting a photoetching process and a dielectric film to expose the end surface of the ridge waveguide and protect other parts of the ridge waveguide;

oxidizing the ridge waveguide end face to form an insulating layer;

forming a metal contact window on the ridge waveguide;

negative photoresist photoetching process;

plating gold on the front surface;

a negative glue Lift-off process;

grinding and polishing;

back gold plating;

and coating a film on the end face of the cleavage surface.

Technical Field

The invention relates to the technical field of semiconductor laser, in particular to an edge-emitting high-power laser and a manufacturing method thereof.

Background

The semiconductor high-power laser has wide application in the fields of industrial manufacturing, laser radar, sensing, communication, aerospace and the like. Because of the advantage that the cavity length of the edge-emitting laser is easy to extend, the edge-emitting laser is more suitable for manufacturing high-power lasers, and the existing semiconductor high-power lasers generally adopt an edge-emitting structure, namely, the light-emitting surface is the end surface of a waveguide.

The cavity surface of the edge-emitting laser is generally a cleavage surface of a semiconductor crystal, and since the cleavage surface of the crystal is very flat and smooth like a mirror surface and is a good light reflecting surface, two cleavage end surfaces of a chip naturally form the cavity surface of the resonant cavity of the edge-emitting laser. In the actual operation process, the two cleavage surfaces are also subjected to coating treatment, on one hand, the end surfaces are protected, and on the other hand, the resonant cavity is optimized and the luminous efficiency is improved. However, with the further increase of the laser power, despite the protection of the facet coating, the cavity facet burn-out (COMD) of the laser is still a difficult problem, which limits the reliability of the semiconductor high-power laser and also limits the further increase of the laser power. The main causes of cavity surface burnout (COMD) are two:

on one hand, the cavity surface is an interface, the interface has a deep energy level, and the deep energy level can absorb the light excited and radiated by the laser to generate heat;

in addition, the vicinity of the cavity surface also emits light due to carrier injection, and heat is also generated. These two heat sources cause the temperature near the facet to rise sharply, and when the power of the laser is increased to a certain value, the facet will burn out due to overheating.

The factor determining the cavity surface burnout is mainly the power density, the larger the power density is, the more serious the end surface heating is, and the more likely the COMD occurs. Thus, to date, whether single mode or multimode lasers, COMD remains a problem that plagues all manufacturers of high power laser chips.

Disclosure of Invention

In view of the above, it is desirable to provide an edge-emitting high-power laser and a method for manufacturing the same, so as to solve the problem that the laser cavity surface of the edge-emitting high-power laser is easy to burn.

An edge-emitting high power laser comprising:

an N-type substrate;

the N-type buffer layer is arranged on the N-type substrate;

the N-type covering layer is arranged on the N-type buffer layer;

the lower waveguide layer is arranged on the N-type covering layer and is undoped;

the active region is arranged on the lower waveguide layer and is undoped;

the upper waveguide layer is arranged on the active region and is undoped;

the P-type covering layer is arranged on the upper waveguide layer, two end faces of the P-type covering layer are respectively provided with an insulating layer, the insulating layers are used for limiting the injection of current carriers into the end faces of the waveguide, the P-type covering layer contains a high-aluminum component layer, and the high-aluminum component layer is oxidized to form the insulating layers at two ends of the P-type covering layer;

a P-type ohmic contact layer disposed on the P-type cladding layer,

and the P-type covering layer and the P-type ohmic contact layer form a ridge waveguide in a ridge shape through etching.

Further, the above edge-emitting high power laser, wherein the ridge waveguide is etched to a lower portion of the P-type cladding layer.

Further, in the edge-emitting high-power laser, the high-aluminum component layer is made of AlGaAs or InGaAlAs.

Further, in the edge-emitting high-power laser, the upper waveguide layer and the lower waveguide layer have a forbidden bandwidth higher than that of the active region.

Further, the above edge-emitting high power laser, wherein the refractive index of the material of the upper waveguide layer and the lower waveguide layer is lower than that of the active region.

Further, in the edge-emitting high-power laser, the thickness of the insulating layer is 50-200 nm.

Further, in the edge-emitting high-power laser, the extension length of the insulating layer in the P-type covering layer is 20-200 um.

The embodiment of the present invention further provides a method for manufacturing an edge-emitting high-power laser, including:

photoetching and positioning a ridge waveguide on an edge-emitting high-power laser main body, and etching the ridge waveguide, wherein the edge-emitting high-power laser main body comprises the N-type substrate, the N-type buffer layer, the N-type covering layer, the lower waveguide layer, the active region, the upper waveguide layer, the P-type covering layer and the P-type ohmic contact layer;

coating a dielectric layer;

corroding the end surface part of the ridge waveguide by adopting a photoetching process and a dielectric film to expose the end surface of the ridge waveguide and protect other parts of the ridge waveguide;

oxidizing the ridge waveguide end face to form an insulating layer;

forming a metal contact window on the ridge waveguide;

negative photoresist photoetching process;

plating gold on the front surface;

a negative glue Lift-off process;

grinding and polishing;

back gold plating;

and coating a film on the end face of the cleavage surface.

The edge-emitting high-power laser is oxidized on the end face of the ridge waveguide to form an insulating layer, and the injection of current carriers near the end face can be limited through the insulating layer, so that the end face heating is reduced, the cavity face of the laser is prevented from being burnt by heating, and the power and the reliability of the laser are improved.

Drawings

FIG. 1 is a front view of an edge-emitting high power laser in an embodiment of the present invention;

FIG. 2 is a schematic perspective view of an edge-emitting high-power laser according to an embodiment of the present invention;

fig. 3 is a flow chart of a method for manufacturing an edge-emitting high-power laser in an embodiment of the invention.

The main elements are indicated by symbols.

N-type substrate	11		Upper waveguide layer	16
					N-type buffer layer	12		P-type cladding layer	17
N-type cladding layer	13		P-type ohmic contact layer	18
					Lower waveguide layer	14		Insulating layer	19
Active region	15

Detailed Description

To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Embodiments of the invention are presented in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, this embodiment is provided so that this disclosure will be thorough and complete.

It will be understood that when an element is referred to as being "secured to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "left," "right," and the like as used herein are for illustrative purposes only.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.

Referring to fig. 1 and 2, an edge-emitting high-power laser according to an embodiment of the present invention includes an N-type substrate 11, an N-type buffer layer 12, an N-type cladding layer 13, a lower waveguide layer 14, an active region 15, an upper waveguide layer 16, a P-type cladding layer 17, and a P-type ohmic contact layer 18. The N-type buffer layer 12 is disposed on the N-type substrate 11, the N-type cladding layer 13 is disposed on the N-type buffer layer 12, the lower waveguide layer 14 and the active region 15 are both disposed on the N-type cladding layer 13, in specific implementation, the active region 15 is formed on the lower waveguide layer 14, the upper waveguide layer 16 is disposed on the active region 15, the P-type cladding layer 17 is disposed on the upper waveguide layer 16, and the P-type ohmic contact layer 18 is disposed on the P-type cladding layer 17.

The N-type substrate 11 is of N conductivity type, and GaAs, InP, or the like can be used as a material thereof.

The N-type buffer layer 12 is grown on the upper surface of the substrate, and the material thereof may be GaAs or InP.

The upper waveguide layer 16 and the intermediate active region 15 are both made of undoped semiconductor material, and the lower waveguide layer 14 is made of low N-type or undoped semiconductor material.

Preferably, the materials of upper waveguide layer 16 and lower waveguide layer 14 have a forbidden band width generally higher than that of active region 15, so that light emitted from active region 15 is not absorbed by upper waveguide layer 16 and lower waveguide layer 14. Meanwhile, the refractive index of the material of upper waveguide layer 16 and lower waveguide layer 14 is generally lower than that of active region 15, so that the desired laser device can be formed by optimizing the design of waveguide layers and active region 15 in the growth direction.

In the direction of material growth, the optical field is mainly distributed in the undoped waveguide region and the active region 15, the total thickness and refractive index distribution of these regions determine the optical mode field distribution in this direction, the total thickness of these regions in a single mode laser is generally within 500nm, and a multimode laser can be thicker. The center of the active region 15 is a light emitting region, the light emitting region comprises a light emitting quantum well and a barrier layer thereof, the number of the quantum wells is determined according to the requirements of the device, generally, a laser with a small cavity length needs more quantum wells, so that the optical gain of the unit length is strong, and the threshold current density of the laser is small; however, the cavity length of the high-power laser is selected to be longer due to the heat dissipation requirement, and in this case, the single quantum well structure is more suitable, so that the threshold current density can be reduced.

The upper waveguide layer 16 is located above the active region 15, and the upper waveguide layer 16 is made of undoped materials such as AlGaAs, AlGaN, GaAsP, InP, AlGaInP, or AlGaInAs.

The P-type ohmic contact layer 18 is made of highly doped GaAs, InGaAs or InP material.

The P-type cladding layer 17 is made of high-doping materials such as AlGaAs, AlGaN, GaAsP, InGaAsP, AlGaInP or AlGaInAs.

The P-type cladding layer 17 and the P-type ohmic contact layer 18 are stacked, and a ridge waveguide having a ridge shape is formed by an etching process. The specific position of the ridge waveguide etching needs to be optimized and simulated according to the material structure, and the ridge waveguide of the edge-emitting high-power laser is deeply etched to the lower part of the P-type covering layer 17.

The mode field distribution parallel to the direction of the epitaxial material is generally confined by a ridge waveguide. Similarly, the difference between single mode and multi-mode in this direction is very large, the ridge waveguide width of the single mode laser is about 3-5 microns, and the multi-mode is more than 100 microns.

The P-type cladding layer 17 has a certain thickness, and a multi-layer epitaxial structure can be subdivided in the cladding layer, wherein the multi-layer epitaxial structure comprises a high-alumina component layer, and insulating layers are formed at two ends of the P-type cladding layer 17 through oxidizing the high-alumina component layer. The high-aluminum component layer can be made of AlGaAs or InGaAlAs material, for example, and the high-aluminum component layer is oxidized to form Al₂O₃An insulating layer. The Al₂O₃The insulating layer has limited manufacturing use for current and optical field, and especially has strong limiting effect on current.

The insulating layers 19 at the two ends of the P-type covering layer 17 can limit current injection near the end face of the waveguide, so that the heating degree of the cavity surface under the same output power is reduced, the risk of cavity surface burnout is reduced, the stability and reliability of the cavity surface of the laser are improved, and the maximum power density which can be borne by the cavity surface is improved.

The purpose of this insulating layer 19 is only to limit the end-face current injection, with limited influence on the light field, and therefore does not need to be very thick, typically between 50-200 nm. The length over which the insulating layer 19 extends can be optimized according to the design, in particular according to the heat and temperature distribution under operating conditions. Because the heat distribution of two terminal surfaces is different in the actual work, the output terminal surface is more easily generated heat, is more easily burnt, and the length that the oxide layer extends can be longer, therefore the length that two terminal surface oxide layers extend is different. The method is easy to realize, and the lengths of the exposed parts of the end faces before oxidation are different. In specific implementation, the ratio of the total length of the insulating layer 19 to the cavity length should be about 5% or less, and for a high power laser with a cavity length of 3mm, the total extension length of the insulating layer is about 150um, wherein the output end is 100um, and the high reflection end is 50 um.

Forming oxide layers at both ends of the P-type cladding layer 17 to control carrier injection is technically feasible, especially for GaAs-based epitaxial materials. By oxidizing the AlGaAs epitaxial layer of high aluminum (Al) composition, carrier injection near the end face can be effectively prevented. Moreover, the oxidation method is not influenced by the width of the ridge waveguide, so that the method is suitable for multimode lasers with wide ridge waveguides and single-mode lasers with narrow ridge waveguides. The most important GaAs-based single-mode high-power laser in the market is a 980nm optical fiber pump laser, which is one of core devices in optical communication, and is basically imported at present. The structure and the preparation method of the device are suitable for a 980nm single-mode laser, and the power and the reliability of the device are expected to be improved.

Certainly, the new structure and process are not limited to be applied to single-mode lasers, and multimode high-power lasers can also be adopted, and currently, the multimode high-power lasers with the wave bands of 976nm, 940nm, 915nm, more than 800 nanometers and the like widely used in the market can be adopted. Even InP-based materials are feasible, and the wave band range can be expanded to 1200-1700 nm. Due to the advantages of the high-power laser in the aspects of space transmission, optical fiber coupling and the like, a good structure and a preparation method can bring wider opportunities and markets for the field.

Referring to fig. 3, a method for manufacturing a side-emitting high-power laser according to a second embodiment of the present invention is shown, which can be used to manufacture a single-mode laser chip according to any of the above embodiments, and the method for manufacturing a side-emitting high-power laser includes steps S201 to S211.

Step S201, performing photoetching positioning on the ridge waveguide on the edge-emitting high-power laser main body, and etching the ridge waveguide.

The edge-emitting high-power laser main body comprises an N-type substrate 11, an N-type buffer layer 12, an N-type covering layer 13, a lower waveguide layer 14, an active region 15, an upper waveguide layer 16, a P-type covering layer 17 and a P-type ohmic contact layer 18 which are sequentially stacked. In specific implementation, the edge-emitting high-power laser material main body can be formed by epitaxial growth on a corresponding N-type substrate 11 material such as GaAs according to a pre-designed structure by adopting methods such as Molecular Beam Epitaxy (MBE) or Metal Organic Chemical Vapor Deposition (MOCVD).

Step S202, coating a dielectric layer. In the specific implementation, a layer of SiO is plated on the surface of the material₂Or a SiN dielectric film.

And S203, corroding the end surface part of the ridge waveguide by adopting a photoetching process and a dielectric film to expose the end surface of the ridge waveguide and protect other parts of the ridge waveguide.

Step S204, oxidizing the end face of the ridge waveguide to form an insulating layer 19;

and S205, opening a metal contact window on the ridge waveguide.

And step S206, negative photoresist photoetching. Namely, the side surface of the negative glue process forms an inverted trapezoid, so that the subsequent Lift-off is facilitated.

Step S207, gold plating is carried out on the front surface. I.e. gold plating on the surface of the material.

And S208, a negative glue Lift-off process. Wherein, Lift-off is to remove the negative glue and the gold on the negative glue.

And step S209, grinding and polishing. The N-type substrate 11 is polished so that the thickness of the material is reduced from about 500um to about 100um, which is beneficial for the subsequent cleavage and heat dissipation of the active region 15.

Step S210, back surface gold plating.

And step S211, plating a film on the end face of the cleavage surface. In the step, the cleaved end face is coated with an optical film, one side is high-reflection film, and the other side is low-reflection film, so that the maximization of output light is facilitated.

In the manufacturing method of the edge-emitting high-power laser in the embodiment, the end face of the ridge waveguide is oxidized to form the insulating layer, and the injection of carriers near the end face can be limited through the insulating layer, so that the end face heating is reduced, and the power and the reliability of the laser are improved. The manufacturing method of the edge-emitting high-power laser is not influenced by the width of the ridge waveguide, so that the method is suitable for both a multi-mode laser and a single-mode laser.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The above-mentioned embodiments only express the embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the present invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention. Therefore, the protection scope of the present patent shall be subject to the appended claims.