WO2021102722A1

WO2021102722A1 - Single-longitudinal-mode edge-emitting laser with side grating oxidation-confinement structure, and preparation method therefor

Info

Publication number: WO2021102722A1
Application number: PCT/CN2019/121155
Authority: WO
Inventors: 王岩; 罗帅; 季海铭
Original assignee: 江苏华兴激光科技有限公司
Priority date: 2019-11-25
Filing date: 2019-11-27
Publication date: 2021-06-03
Also published as: CN110880675A

Abstract

A single-longitudinal-mode edge-emitting laser with a side grating oxidation-confinement structure, and a preparation method therefor. The single-longitudinal-mode edge-emitting laser with a side grating oxidation-confinement structure comprises an N-electrode layer; a substrate (8) arranged on the N-electrode layer; a lower cover layer (7) arranged on the substrate (8); a lower waveguide layer (6) arranged on the lower cover layer (7); an active region (5) arranged on the lower waveguide layer (6); and a ridge strip structure arranged on the active region (5). The ridge strip structure comprises: an upper waveguide layer (4) arranged on the active region (5); an intermediate high-aluminum component layer (3) arranged on the upper waveguide layer (4); an upper cover layer (2) arranged on the intermediate high-aluminum component layer (3); a contact layer (1) arranged on the upper cover layer (2); and a P-electrode layer (9) arranged on the contact layer (1); and a side grating structure that is arranged on a side portion of the ridge strip structure and is of a groove-shaped periodic structure. The present invention facilitates the realization of efficient current injection and a large-mode-volume fundamental transverse mode, and the selection of a grating in a low-loss mode.

Description

Single-longitudinal-mode side-emitting laser with side grating oxidation restriction structure and preparation method thereof

Technical field

The invention relates to the technical field of optoelectronic device design, in particular to a single longitudinal mode side-emitting laser with a side grating oxidation limiting structure and a preparation method thereof.

Background technique

Semiconductor lasers, also known as laser diodes, are lasers that use semiconductor materials as working materials. Due to the difference in material structure, the specific processes of different types of lasers are quite special. Commonly used working materials are gallium arsenide (GaAs), cadmium sulfide (CdS), indium phosphide (InP), zinc sulfide (ZnS), etc. There are three types of excitation methods: electrical injection, electron beam excitation and optical pumping. Semiconductor laser devices can be divided into homojunctions, single heterojunctions, and double heterojunctions. Homojunction lasers and single heterojunction lasers are mostly pulsed devices at room temperature, while double heterojunction lasers can achieve continuous operation at room temperature.

The semiconductor diode laser is the most practical and important type of laser. It is small in size, long in life, and can be pumped by simple current injection. Its working voltage and current are compatible with integrated circuits, so it can be monolithically integrated with it. And you can also directly modulate the current with a frequency up to several tens of GHz to obtain high-speed modulated laser output. Due to these advantages, semiconductor diode lasers have been widely used in laser communications, optical storage, optical gyroscopes, laser printing, ranging and radar. At the same time, semiconductor lasers can also be used as pump light sources for high-power applications, such as lasers for marking, welding, and cutting.

Edge emission means that the laser emission direction is along the horizontal direction, that is, perpendicular to the material growth direction. If it emits along the growth direction, it is called a vertical surface emitting laser. Because edge-emitting lasers can obtain higher power, efficiency and spectral characteristics, they are currently widely used in the fields of communication and pumping.

Common semiconductor edge-emitting lasers realize fundamental transverse mode operation by narrowing the strip width, and realize single longitudinal mode operation by fabricating a complex grating in the waveguide layer. This refractive index guiding structure has a large resistivity and a horizontal divergence angle of the mode. Large, complex process, low yield.

In view of this, in order to overcome the above technical defects, providing a single longitudinal mode side-emitting laser with a side grating oxidation confinement structure and a preparation method thereof has become an urgent problem to be solved in the art.

Summary of the invention

The purpose of the present invention is to overcome the shortcomings of the prior art and provide a single longitudinal mode side emitting laser with a side grating oxidation limiting structure and a preparation method thereof, which is helpful for high-efficiency current injection, realization of large mode volume fundamental transverse mode, and low loss Realization of mode selection grating.

In order to solve the above technical problems, the technical solution of the present invention is: a single longitudinal mode side emitting laser with a side grating oxidation confinement structure. The difference is that it includes an N electrode layer; a substrate is arranged on the N electrode layer; The cover layer is arranged on the substrate; the lower waveguide layer is arranged on the lower cover layer; the active area is arranged on the lower waveguide layer;

The ridge strip structure is arranged on the active area; the ridge strip structure includes: an upper waveguide layer arranged on the active area; a middle high-aluminum component layer arranged on the upper waveguide layer; an upper cap layer arranged on the active area On the middle high-aluminum component layer; the contact layer is set on the upper cover layer; the P electrode layer is set on the contact layer;

The side grating structure is arranged on the side of the ridge strip structure and has a groove-shaped periodic structure.

According to the above technical solution, the material of the substrate is GaAs or InP, which is N-type or P-type conductivity;

The material of the lower cap layer is AlGaAs, InGaAs, GaAsP, InP, AlGaInP or AlGaInAs, and the doping concentration ranges from 5X10^17/cm^3 to 5X10^18/cm^3, N-type or P-type conductivity;

The material of the lower waveguide layer is AlGaAs, InGaAs, GaAsP, InP, AlGaInP or AlGaInAs, and the doping concentration ranges from 5X10^17/cm^3 to 3X10^18/cm^3, N-type or P-type conductivity;

The active region is an InGaAs/GaAs, InGaAs/AlGaAs, InGaAs/GaAsP multiple quantum well structure, and the center wavelength of the emission spectrum matches the laser lasing wavelength;

The material of the upper waveguide layer is AlGaAs, InGaAs, GaAsP, InP, AlGaInP or AlGaInAs, and the doping concentration ranges from 5X10^17/cm^3 to 3X10^18/cm^3, corresponding to the P-type lower waveguide layer Or N-type conductivity;

The upper cap layer is AlGaAs, InGaAs, GaAsP, InP, AlGaInP or AlGaInAs, and the doping concentration ranges from 5X10^17/cm^3 to 5X10^18/cm^3, P-type or N-type conductivity;

The contact layer is made of P-type or N-type conductive highly doped GaAs or InGaAs material, with a thickness of 5nm to 200nm, and a doping concentration of 1X10^19/cm^3 to 5X10^19/cm^3.

According to the above technical scheme, the material of the middle high-aluminum composition layer is AlGaAs or AlInAs; an Al ₂ O ₃ insulating layer can be formed under the condition of high temperature and humid oxygen, changing from a high refractive index to a low refractive index, which is used to limit current and light. field.

According to the above technical solution, the side grating structure expands into the ridge strip structure, and the inner grating is formed by cloning.

A method for preparing a single longitudinal mode side-emitting laser with a side grating oxidation confinement structure, which is characterized in that the steps are:

Step 1). On the epitaxial material, photoetch a striped pattern with side gratings, and etch the epitaxial layer with a high aluminum component layer to the upper waveguide layer; the epitaxial material includes a substrate layered sequentially from bottom to top, Lower cover layer, lower waveguide layer, active area, upper waveguide layer, middle high aluminum component layer, upper cover layer and contact layer;

Step 2). Wet oxygen oxidation: horizontally oxidize the middle high-aluminum component layer to the required depth; at this time, the outside of the middle high-aluminum component layer becomes insulating alumina, and the side grating structure expands into the ridge stripe structure. The clone forms an internal grating.

Step 3), grow an insulating layer, and etch the upper electrode window;

Step 4), photolithography and metal stripping to form a P electrode;

Step 5), wafer thinning;

Step 6), evaporate the N-type electrode and anneal.

According to the above technical scheme, in the step 2), the high temperature of 400-470 degrees is used, and the 5:95 H2 and N2 mixed gas is used as the water vapor carrier gas to oxidize the high-aluminum component layer under a pressure of 10 m Bar. The middle high aluminum component layer is oxidized, and an oxide strip is formed in the middle, which limits the current and light field.

According to the above technical solution, in the step 3), the insulating layer material is silicon dioxide or silicon nitride, and the thickness is 200-300 nm.

According to the above technical solution, in the step 4), the P electrode is thick gold with a thickness of 1 to 3 microns to improve thermal characteristics.

According to the above technical solution, in the step 5), the wafer is thinned to 130-150 microns.

According to the above technical solution, in the step 6), the N-type electrode material is formed by evaporating AuGeNi/Au alloy by electron beam, and the thickness is 100-500 nm.

Based on the above solution, the present invention discloses a method for realizing a single longitudinal mode side-emitting laser that combines a side grating and an oxidation limiting process. The purpose is to provide a low-loss grating realization method for a semiconductor side-emitting laser, using wet oxygen Oxidation forms an insulating region and a low-refractive-index waveguide region. This method facilitates high-efficiency current injection, realization of large mode volume fundamental transverse modes, and realization of low-loss mode selection gratings. In the implementation process of this technology, expensive secondary epitaxial material growth and ion implantation technology are not required.

Description of the drawings

FIG. 1 is a schematic diagram of the overall structure of a laser according to an embodiment of the present invention;

Figure 2 is a schematic flow chart of a laser manufacturing method according to an embodiment of the present invention;

Fig. 3 is a schematic diagram of the structure of the exceptionally extended material in the implementation of the present invention;

Among them: 1-contact layer, 2-upper cover layer, 3-middle high aluminum component layer (31-Al ₂ O ₃ insulating layer), 4-upper waveguide layer, 5-active area, 6-lower waveguide layer, 7-lower cover layer, 8-substrate, 9-P electrode.

Detailed ways

In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, but not used to limit the present invention.

In the following, many aspects of the present invention will be better understood with reference to the drawings. The parts in the drawings are not necessarily drawn to scale. Instead, the focus is on clearly describing the components of the invention. In addition, in several views in the drawings, the same reference numerals indicate corresponding parts.

The word "exemplary" or "illustrative" as used herein means serving as an example, instance, or illustration. Any embodiment described herein as "exemplary" or "illustrative" is not necessarily construed as being preferred or advantageous over other embodiments. All the embodiments described below are exemplary embodiments. These exemplary embodiments are provided to enable those skilled in the art to make and use the embodiments of the present disclosure and are not intended to limit the scope of the present disclosure. The scope of the present disclosure is determined by Claims are defined. In other embodiments, well-known features and methods are described in detail so as not to obscure the present invention. For the purpose of the description herein, the terms "upper", "lower", "left", "right", "front", "rear", "vertical", "horizontal" and their derivatives will be oriented as shown in Figure 1. The invention is related. Moreover, there is no intention to be limited by any expressed or implied theory given in the foregoing technical field, background technology, summary of the invention or the following detailed description. It should also be understood that the specific devices and processes shown in the drawings and described in the following specification are simple exemplary embodiments of the inventive concept defined in the appended claims. Therefore, the specific dimensions and other physical features related to the embodiments disclosed herein should not be construed as restrictive unless the claims expressly state otherwise.

Please refer to Figure 1 to Figure 3, the present invention is a side grating oxidation confinement structure single longitudinal mode edge emitting laser, the difference lies in: it includes an N electrode layer; a substrate 8 arranged on the N electrode layer; lower cover layer 7. Set on the substrate 8; the lower waveguide layer 6 is set on the lower cover layer 7; the active area 5 is set on the lower waveguide layer 6;

The ridge strip structure is arranged on the active area 5; the ridge strip structure includes: an upper waveguide layer 4 arranged on the active area 5; a middle high-aluminum component layer 3 arranged on the upper waveguide layer 4; The upper cover layer 2 is arranged on the middle high-aluminum component layer 3; the contact layer 1 is arranged on the upper cover layer 2; the P electrode layer 9 is arranged on the contact layer 1;

The side wall of the main structure is provided with an insulating film (that is, an insulating layer) for protection.

Preferably, the material of the substrate 8 is GaAs or InP, etc., which is N-type or P-type conductivity;

The material of the lower cap layer 7 is AlGaAs, InGaAs, GaAsP, InP, AlGaInP or AlGaInAs, etc., and the doping concentration ranges from 5X10^17/cm^3 to 5X10^18/cm^3, N-type or P-type conductivity;

The material of the lower waveguide layer 6 is AlGaAs, InGaAs, GaAsP, InP, AlGaInP or AlGaInAs, etc., and the doping concentration ranges from 5X10^17/cm^3 to 3X10^18/cm^3, N-type or P-type conductivity;

The active region 5 is a multi-quantum well structure such as InGaAs/GaAs, InGaAs/AlGaAs, InGaAs/GaAsP, etc. The center wavelength of the emission spectrum matches the laser lasing wavelength; the multi-quantum well region is a strain-compensating structure, and refraction The rate is higher than that of the waveguide layer (including the upper waveguide layer 4 and the lower waveguide layer 6).

The material of the upper waveguide layer 4 is AlGaAs, InGaAs, GaAsP, InP, AlGaInP or AlGaInAs, etc., and the doping concentration ranges from 5X10^17/cm^3 to 3X10^18/cm^3, corresponding to the lower waveguide layer being P-type or N-type conductivity;

The upper cap layer 2 is AlGaAs, InGaAs, GaAsP, InP, AlGaInP or AlGaInAs, etc., and the doping concentration ranges from 5X10^17/cm^3 to 5X10^18/cm^3, P-type or N-type conductivity;

The contact layer 1 is a P-type or N-type conductive highly doped GaAs or InGaAs material, with a thickness of 5 nm to 200 nm, and a doping concentration of 1X10^19/cm^3 to 5X10^19/cm^3.

Preferably, the material of the middle high-aluminum component layer 3 is AlGaAs or AlInAs; the Al component is 0.95-0.99; the Al ₂ O ₃ insulating layer 31 can be formed under the condition of high temperature and humid oxygen, changing from high refractive index to low The refractive index changes from a high refractive index of 3 (around) to a low refractive index of 1.75 (around), which is used to limit the current and light field. The thickness is less than 50nm and is used to form a weak refractive index guide. A high-aluminum component layer is added, which can be used for current limiting and forming a weak refractive index guiding structure after partial oxidation. The combination with side grating can realize the selection of the longitudinal mode of the laser.

Specifically, the side grating structure is further oxidized, expands into the ridge strip structure, and clones to form an internal low-loss grating structure.

Step 1). On the epitaxial material, photoetch a strip pattern with side gratings, and etch the epitaxial layer through the middle high-aluminum component layer 3 to the upper waveguide layer 4; the epitaxial material includes layers stacked sequentially from bottom to top The substrate 8, the lower cap layer 7, the lower waveguide layer 6, the active region 5, the upper waveguide layer 4, the middle high-aluminum component layer 3, the upper cap layer 2, and the contact layer 1; the middle high-aluminum component layer 3 is the The most important feature of epitaxial materials, its composition and thickness determine the current and optical field confinement effects.

Step 2), wet oxygen oxidation: horizontally oxidize the middle high-aluminum component layer 3 to the required depth; at this time, the outside of the middle high-aluminum component layer 3 becomes insulating aluminum oxide, with a refractive index of about 1.75, which is very sensitive to current and light fields. Both have a restrictive effect, which is a strong restriction on the current and a weak restriction on the light field, which is conducive to the expansion of the lateral light field. At the same time, the side grating structure expands into the ridge strip structure, cloning to form an internal grating.

Step 3). Growing an insulating layer, and etching the upper electrode window; the side wall of the main structure is exposed, and an insulating film (ie, insulating layer) must be grown as a whole for protection;

Step 4), photolithography and metal stripping to form the P electrode 9;

Step 5), wafer thinning;

Step 6), evaporate the N-type electrode and anneal.

Preferably, in the step 1), the etching process is a combination of dry and wet methods, and the process used is an induction induced plasma etching technology using online monitoring.

Preferably, in the step 2), using a high temperature of 400 to 470 degrees, using a 5:95 H2 and N2 mixed gas as a water vapor carrier gas, the middle high aluminum component layer 3 is oxidized under a pressure of 10 mBar. As a result, the middle high-aluminum component layer 3 is oxidized, and an oxide strip is formed in the middle to limit the current and light field.

Preferably, in the step 3), the insulating layer material is silicon dioxide or silicon nitride, and the thickness is 200-300 nm.

Preferably, in the step 4), the P electrode 9 is thick gold with a thickness of 1 to 3 microns, which is used to improve thermal characteristics.

Preferably, in the step 5), the wafer is thinned to 130-150 microns. It not only guarantees strength, but also facilitates heat dissipation.

Preferably, in the step 6), the N-type electrode material is formed by electron beam evaporation of AuGeNi/Au alloy, and the thickness is 100-500 nm.

The invention discloses a method for realizing a single longitudinal mode side-emitting laser with a side grating oxidation limiting structure, which is suitable for the mode control of a semiconductor side-emitting laser, and is helpful for high-efficiency current injection and realization of a large mode volume fundamental transverse mode. The present invention proposes to introduce a high-aluminum component into a specific thin layer of a conventional side-emitting epitaxial material structure, and through wet oxygen oxidation in a similar surface-emitting laser process, a part of the specific film layer becomes an insulating layer and a low-refractive-index area to realize current limitation And the weak refractive index guiding effect, on the one hand to improve the injection efficiency, on the other hand can reduce the horizontal divergence angle. By fabricating side gratings on both sides of the laser ridge strips, during the oxidation of the high aluminum component, the side gratings move inward and transfer to the inside of the ridge strips, thereby forming a standing wave field with a specific wavelength in the ridge strips away from the surface. In order to realize the selection of the longitudinal mode for single-mode operation, the intensity of the selection of the longitudinal mode can be adjusted, and at the same time, the loss caused by the large roughness of the ridge strip surface can be reduced, and the longitudinal mode selection can be realized by forming a low-loss grating structure.

The above content is a further detailed description of the present invention in combination with specific implementations, and it cannot be considered that the specific implementations of the present invention are limited to these descriptions. For those of ordinary skill in the technical field to which the present invention belongs, a number of simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

The side-grating oxidation confinement structure single longitudinal mode side-emitting laser is characterized in that it includes

N electrode layer;

The substrate is set on the N electrode layer;

The lower cover layer is set on the substrate;

The lower waveguide layer is set on the lower cover layer;

The active area is set on the lower waveguide layer;

The ridge stripe structure is arranged on the active area; the ridge stripe structure includes:

The upper waveguide layer is set on the active area;

The middle high-aluminum component layer is set on the upper waveguide layer;

The upper cover layer is set on the middle high aluminum component layer;

The contact layer is arranged on the upper cover layer;

The P electrode layer is arranged on the contact layer;

The side grating structure is arranged on the side of the ridge strip structure and has a groove-shaped periodic structure.
The single-longitudinal-mode side-emitting laser with a side grating oxidation confinement structure according to claim 1, characterized in that:

The material of the substrate is GaAs or InP, which is N-type or P-type conductivity;

The material of the lower cap layer is AlGaAs, InGaAs, GaAsP, InP, AlGaInP or AlGaInAs, and the doping concentration ranges from 5X10^17/cm^3 to 5X10^18/cm^3, N-type or P-type conductivity;

The material of the lower waveguide layer is AlGaAs, InGaAs, GaAsP, InP, AlGaInP or AlGaInAs, and the doping concentration ranges from 5X10^17/cm^3 to 3X10^18/cm^3, N-type or P-type conductivity;

The active region is an InGaAs/GaAs, InGaAs/AlGaAs, InGaAs/GaAsP multiple quantum well structure, and the center wavelength of the emission spectrum matches the laser lasing wavelength;

The material of the upper waveguide layer is AlGaAs, InGaAs, GaAsP, InP, AlGaInP or AlGaInAs, and the doping concentration ranges from 5X10^17/cm^3 to 3X10^18/cm^3, corresponding to the P-type lower waveguide layer Or N-type conductivity;

The upper cap layer is AlGaAs, InGaAs, GaAsP, InP, AlGaInP or AlGaInAs, and the doping concentration ranges from 5X10^17/cm^3 to 5X10^18/cm^3, P-type or N-type conductivity;

The contact layer is made of P-type or N-type conductive highly doped GaAs or InGaAs material, with a thickness of 5nm to 200nm, and a doping concentration of 1X10^19/cm^3 to 5X10^19/cm^3.
The single-longitudinal-mode side-emitting laser with a side grating oxidation confinement structure according to claim 1, wherein the material of the middle high-aluminum composition layer is AlGaAs or AlInAs; Al 2 O 3 can be formed under the condition of high temperature and humid oxygen. The insulating layer, which changes from a high refractive index to a low refractive index, is used to limit the current and light field.
The single-longitudinal-mode side-emitting laser with a side grating oxidation confinement structure according to claim 1, wherein the side grating structure expands into the ridge strip structure to form an internal grating by cloning.
The method for manufacturing a single longitudinal mode side-emitting laser with a side grating oxidation confinement structure according to any one of claims 1 to 4, characterized in that the steps are:

Step 1). On the epitaxial material, photoetch a strip pattern with side gratings, and etch the epitaxial layer through the middle high-aluminum component layer to the upper waveguide layer; the epitaxial material includes substrates stacked sequentially from bottom to top , Lower cover layer, lower waveguide layer, active area, upper waveguide layer, middle high aluminum component layer, upper cover layer and contact layer;

Step 2), wet oxygen oxidation: horizontally oxidize the middle high-aluminum component layer to the required depth; at this time, the outer side of the middle high-aluminum component layer becomes insulating alumina, and the side grating structure expands into the ridge stripe structure. The clone forms an internal grating.

Step 3), grow an insulating layer, and etch the upper electrode window;

Step 4), photolithography and metal stripping to form a P electrode;

Step 5), wafer thinning;

Step 6), evaporate the N-type electrode and anneal.
The method for manufacturing a single longitudinal mode side-emitting laser with a side grating oxidation confinement structure according to claim 5, characterized in that: in the step 2), a high temperature of 400 to 470 degrees is used and a mixed gas of H2 and N2 of 5:95 is used. As a water vapor carrier gas, the middle high-aluminum component layer is oxidized under a pressure of 10 m Bar, so that the middle high-aluminum component layer is oxidized, and an oxide strip is formed in the middle to limit the current and light field.
The method for manufacturing a single-longitudinal-mode side-emitting laser with a side grating oxidation confinement structure according to claim 5, characterized in that: in step 3), the insulating layer material is silicon dioxide or silicon nitride with a thickness of 200 ~300nm.
The method for manufacturing a single longitudinal mode edge-emitting laser with a side grating oxidation confinement structure according to claim 5, characterized in that: in the step 4), the P electrode is thick gold with a thickness of 1 to 3 microns for Improve thermal characteristics.
The method for manufacturing a single longitudinal mode side-emitting laser with a side grating oxidation confinement structure according to claim 5, wherein in step 5), the wafer is thinned to 130-150 microns.
The method for manufacturing a single longitudinal mode edge-emitting laser with a side grating oxidation confinement structure according to claim 5, wherein in step 6), the N-type electrode material is formed by electron beam evaporation of AuGeNi/Au alloy, The thickness is 100-500nm.