WO2021056617A1

WO2021056617A1 - Semiconductor laser and carrier injection method therefor

Info

Publication number: WO2021056617A1
Application number: PCT/CN2019/111045
Authority: WO
Inventors: 王俊; 赵智德; 谭少阳; 程洋
Original assignee: 苏州长光华芯半导体激光创新研究院有限公司
Priority date: 2019-09-26
Filing date: 2019-10-14
Publication date: 2021-04-01
Also published as: CN110739605A

Abstract

A semiconductor laser and a carrier injection method therefor. The method comprises: preparing a semiconductor laser epitaxial structure on a substrate, and obtaining an epitaxial structure wafer (S1); preparing a ridge-shaped structure of the semiconductor laser on the wafer (S2); preparing a dielectric film on the ridge-shaped structure (S3); etching the dielectric film on a ridge surface of the ridge-shaped structure to form a dielectric film which is distributed in a non-uniform shape along a longitudinal direction (S4); preparing an electrode on the dielectric film (S5); cleaving the wafer, and respectively preparing an anti-reflection film and a high-reflection film at a front end and a rear end of a cleaved surface (S6); and carrying out carrier injection from an anti-reflection film cavity surface to a high-reflection film cavity surface (S7). By controlling the shape of the dielectric film on the ridge surface, non-uniform injection of current along the longitudinal direction of the ridge is realized, and therefore, carrier non-uniform distribution caused by long cavity length and the reflectivity difference of the cavity surfaces at the two ends is offset, the distribution uniformity of gains of the semiconductor laser along a longitudinal direction under a working state is improved, and the light output power of the semiconductor laser is improved.

Description

Semiconductor laser and its carrier injection method

Technical field

This application relates to the technical field of semiconductor lasers, in particular to a semiconductor laser and a carrier injection method thereof.

Background technique

The traditional semiconductor laser adopts a uniform carrier injection scheme, and the electrodes are uniformly distributed along the longitudinal direction, so that the carrier density of the entire ridge injection is completely consistent. In order to improve the slope efficiency and maximize the output power, the two ends of the laser will be treated with anti-reflection (AR) film and high-reflection (HR) film respectively, so that the laser is concentrated on the end of the anti-reflection film. When the injection current is less than the threshold current, the photon density in the semiconductor laser cavity is very low, so it shows a uniform distribution along the longitudinal direction (AR cavity surface to HR cavity surface); when the injection current is greater than the threshold current, the laser starts lasing. The photon density in the resonant cavity will gradually increase as the injection current increases, and the photon density in the laser resonant cavity shows a gradual decrease along the longitudinal direction (AR cavity surface to HR cavity surface). Due to the effect of stimulated emission, the higher the photon density, the faster the carrier consumption rate and the lower the carrier density. Therefore, the carrier density will gradually increase from the AR cavity surface to the HR cavity surface. Trend, the uneven distribution of the carrier density along the longitudinal direction will cause the uneven distribution of the gain in the longitudinal direction, leading to the degradation of the semiconductor laser performance and the decrease of the optical output power.

Summary of the invention

Therefore, the present application provides a semiconductor laser and a carrier injection method thereof, which overcomes the non-uniform distribution of carrier density along the longitudinal direction in the prior art, which can cause the non-uniform distribution of gain in the longitudinal direction, which leads to the degradation of semiconductor laser performance and light emission. Insufficient output power drop.

In the first aspect, an embodiment of the present application provides a carrier injection method for a semiconductor laser, including: preparing a semiconductor laser epitaxial structure on a substrate to obtain an epitaxial structure wafer; preparing a ridge structure of the semiconductor laser on the wafer ; Preparation of dielectric film on the ridge structure; etching of the dielectric film on the ridge surface of the ridge structure to form a dielectric film with a non-uniform shape distribution along the longitudinal direction; preparation of electrodes on the dielectric film; Carry out cleavage, and prepare anti-reflection film and high-reflection film on the front and back ends of the cleavage surface respectively; from the anti-reflection film cavity surface to the high-reflection film cavity surface, carry out carrier injection of the semiconductor laser.

In an embodiment, the step of etching the dielectric film on the ridge surface of the ridge structure to form a dielectric film with a non-uniform shape distribution along the longitudinal direction includes: obtaining a current carrier when the semiconductor laser is uniformly injected into the electrode According to the non-linear distribution curve of carriers, the ridge surface of the ridge structure is divided into multiple regions along the longitudinal direction, and the non-uniform shape distribution of the dielectric film in each region The area ratio gradually increases from the surface of the anti-reflective film cavity to the surface of the high-reflective film cavity.

In one embodiment, the area of the dielectric film with non-uniform shape distribution in each section of the region is not completely the same.

In one embodiment, the length of the division of the region close to the cavity surface of the high-reflective film is shorter than the length of the division of the region close to the cavity surface of the anti-reflective film.

In an embodiment, the length of the dielectric film in each region is determined according to the cavity length of the semiconductor laser, the reflectivity of the anti-reflection film cavity surface and the high-reflection film cavity surface, the working current and the nonlinear distribution curve of carriers.

In a second aspect, the present application provides a semiconductor laser, including: a substrate; a semiconductor laser epitaxial structure formed on the substrate; a ridge structure formed on the epitaxial structure; a dielectric film formed on the ridge Structurally; a dielectric film with a longitudinal non-uniform shape distribution is formed above the ridge surface of the ridge structure; an electrode is formed on the dielectric film; an anti-reflection film and a high-reflection film are formed on the front and rear surfaces of the cleavage surface of the epitaxial structure .

In an embodiment, the area ratio of the dielectric film distributed in a longitudinally non-uniform shape gradually increases from the cavity surface of the anti-reflection film to the cavity surface of the high-reflection film.

In one embodiment, the areas of the dielectric films with longitudinal non-uniform shape distribution are not completely the same.

In an embodiment, the shape of the dielectric film with longitudinal non-uniform shape distribution is polygonal, circular or elliptical.

The technical solution of this application has the following advantages:

The carrier injection method of the semiconductor laser provided by this application controls the actual current injection area by controlling the shape of the dielectric film above the ridge surface, and realizes the non-uniform injection of current along the longitudinal direction of the ridge, thereby offsetting the long cavity length and the cavity at both ends. The non-uniform distribution of carriers caused by the difference in surface reflectivity improves the uniformity of the longitudinal distribution of the gain in the working state of the semiconductor laser, and improves the optical output power of the semiconductor laser.

Description of the drawings

In order to more clearly illustrate the specific embodiments of this application or the technical solutions in the prior art, the following will briefly introduce the drawings that need to be used in the specific embodiments or the description of the prior art. Obviously, the appendix in the following description The drawings are some embodiments of the application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work.

Fig. 1 is a flowchart of an example of a carrier injection method of a semiconductor laser provided by an embodiment of the application;

2 is a schematic diagram of a substrate and an epitaxial structure wafer provided by an embodiment of the application;

Figure 3 is a schematic diagram of a ridge structure provided by an embodiment of the application;

4 is a schematic diagram of a dielectric film provided by an embodiment of the application;

5 is a schematic diagram of a dielectric film with a non-uniform shape distribution provided by an embodiment of the application;

FIG. 6 is a schematic diagram of an electrode structure provided by an embodiment of the application;

FIG. 7 is a schematic diagram of an AR cavity surface and an HR cavity surface provided by an embodiment of the application;

FIG. 8 is an example flow chart of forming a dielectric film with a non-uniform shape distribution according to an embodiment of the application;

FIG. 9 is a schematic diagram of a non-linear distribution curve diagram of carriers when the electrodes are uniformly injected according to an embodiment of the application; FIG.

10 is a cross-sectional view of a dielectric film with a non-uniform shape distribution provided by an embodiment of the application;

FIG. 11 is a comparison diagram of the longitudinal distribution of the carrier concentration of the ridges divided by equal length and unequal length according to the embodiment of the application;

FIG. 12 is a schematic structural diagram of a semiconductor laser provided by an embodiment of the application.

detailed description

The technical solution of the present application will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of this application.

In the description of this application, it should be noted that the terms "installation", "connection", and "connection" should be understood in a broad sense, unless otherwise clearly specified and limited. For example, it can be a fixed connection or a detachable connection. Connected or integrally connected; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be the internal connection of the two components, it can be a wireless connection, or it can be a wired connection connection. For those of ordinary skill in the art, the specific meanings of the above-mentioned terms in this application can be understood under specific circumstances.

In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

Example 1

An embodiment of the present application provides a carrier injection method for a semiconductor laser, as shown in FIG. 1, including:

Step S1: Prepare a semiconductor laser epitaxial structure on a substrate to obtain an epitaxial structure wafer.

In the embodiment of the present application, the existing MOCVD, MBE and other equipment can be used to grow the semiconductor laser epitaxial structure on the substrate, as shown in FIG. 2, to obtain the laser epitaxial structure wafer.

Step S2: preparing the ridge structure of the semiconductor laser on the wafer.

In the embodiment of the present application, a ridge structure is prepared on a wafer by photolithography. As shown in FIG. 3, the ridge structure can be a trapezoidal structure with a height in the middle part and two sides. For limitation, in other embodiments, it may be a ridge structure with other shapes.

Step S3: preparing a dielectric film on the ridge structure.

In the embodiment of the present application, the material of the dielectric film may be SiO ₂ or SiN. As shown in FIG. 4, the prepared dielectric film covers the entire surface of the ridge structure.

Step S4: etching the dielectric film on the ridge surface of the ridge structure to form a dielectric film with a non-uniform shape distribution along the longitudinal direction.

In the embodiment of the present application, the dielectric film is etched on the ridge surface of the ridge structure by photolithography, so that the dielectric film on the ridge surface has a non-uniform shape distribution, so that it can be evenly distributed during carrier injection. The non-uniform shape distribution of the dielectric film formed on it is shown in Figure 5.

Step S5: preparing electrodes on the dielectric film.

In the embodiment of the present application, as shown in FIG. 6, an electrode structure formed by a metal electrode is formed on a dielectric thin film by deposition.

Step S6: The wafer is cleaved, and anti-reflection films and high-reflection films are prepared on the front and back ends of the cleaved surface respectively.

In the embodiment of the present application, as shown in FIG. 7, after the wafer is cleaved, an anti-reflection (AR) film and a high-reflection (HR) film can be formed on the front and rear ends of the cleavage surface by evaporation. Form AR cavity surface and HR cavity surface.

Step S7: Perform carrier injection of the semiconductor laser from the surface of the anti-reflective film cavity to the surface of the high-reflective film cavity.

The carrier injection method of a semiconductor laser provided in this application is to etch the dielectric film on the ridge surface. Only the surface of the wafer that is not covered with the dielectric film on the ridge can contact the metal electrode, thus along the longitudinal direction. Non-uniform carrier injection can be obtained, and the patterned electrode is used to achieve non-uniform injection of carriers, thereby offsetting the non-uniform distribution of carriers caused by the long cavity length and the difference in the reflectivity of the cavity surfaces at both ends, and improving the working state of the semiconductor laser The uniformity of the lower gain along the longitudinal distribution improves the optical output power of the semiconductor laser.

In an embodiment, the specific process of performing step S4, as shown in FIG. 8, includes:

Step S41: Obtain a nonlinear distribution curve of carriers when the semiconductor laser is uniformly injected into the electrode.

In practice, when the injection current is greater than the threshold current, the laser starts lasing. The photon density in the cavity will gradually increase with the increase of the injection current, and the photon density in the laser cavity is along the longitudinal direction (AR cavity surface to HR cavity The surface) shows a gradually decreasing trend, resulting in a lower carrier concentration on the AR side, and a higher carrier concentration on the high-reflective film (HR) side, as shown in Figure 9 When uniformly injected into the electrode, the carrier is a non-linear distribution curve.

Step S42: According to the non-linear distribution curve of carriers, the ridge surface of the ridge structure is divided into multiple sections along the longitudinal direction, and the area of the non-uniformly distributed dielectric film in each section is It gradually increases from the surface of the anti-reflective film cavity to the surface of the high-reflective film cavity.

In the embodiment of the present application, the area ratio of the dielectric film is the area of the dielectric film/the area of the small area. As shown in FIG. 10, the ridge structure is divided into three parts from left to right, and the middle part is the ridge surface. During the photolithography of the dielectric film, the dielectric film above the ridge surface is not completely removed and is divided into several regions. The area of the dielectric film distributed in non-uniform shapes in each region is not exactly the same, and along the AR The longitudinal direction from the cavity surface to the HR cavity surface increases linearly. The length of the region division close to the high-reflection film cavity surface is shorter than the length of the region division close to the anti-reflection film cavity surface. It depends on the cavity length of the semiconductor laser and the anti-reflection film cavity surface. And the non-linear distribution curve of high reflection film cavity surface reflectance, working current and carrier determine the length of the dielectric film in each region. As shown in FIG. 11, by adopting an optimized non-equal length division method, the present application can effectively improve the uniformity of the carrier concentration and gain along the longitudinal distribution, by increasing the optical output power of the semiconductor laser by 10%.

Example 2

An embodiment of the present application provides a semiconductor laser, as shown in FIG. 12, comprising: a substrate; a semiconductor laser epitaxial structure formed on the substrate; a ridge structure formed on the epitaxial structure; a dielectric film formed on the substrate On the ridge structure; a dielectric film with a longitudinal non-uniform shape distribution is formed above the ridge surface of the ridge structure; an electrode is formed on the dielectric film; an anti-reflection film and a high-reflection film are formed on the cleavage of the epitaxial structure The front and rear faces of the face.

In the embodiment of the present application, the area ratio of the dielectric film distributed in the longitudinal non-uniform shape gradually increases along the direction from the cavity surface of the anti-reflective film to the cavity surface of the high-reflection film, and the area of the dielectric film distributed in the longitudinal non-uniform shape is different. The arrangement of the dielectric film with exactly the same, non-uniform shape distribution is shown in Figure 10. The ridge structure is divided into three parts from left to right. The middle part is the ridge surface, and the area close to the HR cavity surface is divided into long sections. The region near the AR cavity surface is divided into longer length regions. The specific length should be determined according to the laser cavity length, the reflectivity of the cavity surfaces at both ends, the operating current, and the carrier distribution curve. The dielectric film that is not etched in FIG. 10 is rectangular, which is only an example, and is not limited to this. In other embodiments, it may be elliptical, circular, or other polygonal shapes.

In the semiconductor laser provided by the embodiment of the present application, the shape of the non-uniformly distributed dielectric film is arranged above the ridge surface to control the actual current injection area, so as to realize the non-uniform injection of current along the longitudinal direction of the ridge, thereby offsetting the long cavity length and both ends. The non-uniform distribution of carriers caused by the difference in the reflectivity of the cavity surface improves the uniformity of the longitudinal distribution of the gain in the working state of the semiconductor laser, and improves the optical output power of the semiconductor laser.

Obviously, the foregoing embodiments are merely examples for clear description, and are not intended to limit the implementation manner. For those of ordinary skill in the art, other changes or modifications in different forms can be made on the basis of the above description. It is unnecessary and impossible to list all the implementation methods here. The obvious changes or changes derived from this are still within the scope of protection created by this application.

Claims

A carrier injection method for a semiconductor laser is characterized in that it comprises:

Prepare the semiconductor laser epitaxial structure on the substrate to obtain the epitaxial structure wafer;

Preparation of the ridge structure of the semiconductor laser on the wafer;

Preparation of dielectric film on the ridge structure;

Etching the dielectric film on the ridge surface of the ridge structure to form a dielectric film with a non-uniform shape distribution along the longitudinal direction;

Preparation of electrodes on the dielectric film;

Cleavage the wafer, and prepare anti-reflection film and high-reflection film on the front and back ends of the cleavage surface;

Carrier injection of the semiconductor laser is performed from the surface of the anti-reflective film cavity to the surface of the high-reflective film cavity.
The carrier injection method of a semiconductor laser according to claim 1, wherein the dielectric film on the ridge surface of the ridge structure is etched to form a dielectric film with a non-uniform shape distribution along the longitudinal direction The steps include:

Obtain the nonlinear distribution curve of carriers when the semiconductor laser is uniformly injected into the electrode;

According to the non-linear distribution curve of the carriers, the ridge structure of the ridge structure is divided into multiple regions along the longitudinal direction. The direction from the film cavity surface to the high reflection film cavity surface gradually increases.
The carrier injection method of a semiconductor laser according to claim 2, wherein the area of the dielectric thin film distributed in the non-uniform shape in each region is not completely the same.
The carrier injection method of a semiconductor laser according to claim 3, wherein the length of the region division close to the cavity surface of the high-reflective film is shorter than the length of the region division close to the cavity surface of the anti-reflective film.
The carrier injection method of a semiconductor laser according to claim 3, characterized in that according to the cavity length of the semiconductor laser, the reflectivity of the anti-reflection film cavity surface and the high-reflection film cavity surface, the operating current and the nonlinearity of the carrier The distribution curve determines the length of the dielectric film in each area.
A semiconductor laser, characterized in that it comprises:

Substrate

A semiconductor laser epitaxial structure formed on the substrate;

A ridge structure formed on the epitaxial structure;

A dielectric film formed on the ridge structure;

A dielectric film with longitudinal non-uniform shape distribution is formed above the ridge surface of the ridge structure;

An electrode formed on the dielectric film;

Anti-reflection film and high-reflection film are formed on the front and back ends of the cleavage surface of the epitaxial structure.
7. The semiconductor laser according to claim 6, wherein the area ratio of the dielectric film distributed in the longitudinal non-uniform shape gradually increases from the surface of the anti-reflection film cavity to the surface of the high-reflection film cavity.
7. The semiconductor laser according to claim 6, wherein the areas of the dielectric films distributed in the longitudinal non-uniform shape are not completely the same.
8. The semiconductor laser according to claim 8, wherein the shape of the dielectric film with longitudinal non-uniform shape distribution is polygonal, circular or elliptical.