CN217563042U

CN217563042U - Surface emitting laser

Info

Publication number: CN217563042U
Application number: CN202221419278.9U
Authority: CN
Inventors: 孙维忠; 唐嘉乐; 罗睿永; 邱姝颖; 陈美娜; 王彦楠
Original assignee: Xiamen Sanan Integrated Circuit Co Ltd
Current assignee: Quanzhou San'an Optical Communication Technology Co ltd
Priority date: 2022-06-08
Filing date: 2022-06-08
Publication date: 2022-10-11
Anticipated expiration: 2032-06-08

Abstract

The utility model discloses a surface emitting laser, including substrate, N type DBR, resonance region, restriction layer and the P type DBR that sets up from bottom to top, be equipped with N type electrode on the substrate, the restriction layer is including the current injection region that is located the middle part and being located outlying insulating area, and the P type DBR is piled up by a plurality of reflection stratum and is formed, and the P type DBR includes the outer loop region outside middle zone and the middle zone, and the middle zone is located the current injection region top of restriction layer, the projection area of outer loop region on the restriction layer are located the insulating area of restriction layer, and the at least partial upper surface of at least a pair of reflection stratum of the regional bottom of outer loop is naked and establish to low mesa, is equipped with P type electrode on the outer loop region of P type DBR, and P type electrode covers at least on low mesa. By changing the structure of the P-type electrode, the conductive path in the laser can be optimized, and the stress caused by the oxidation limiting process can be reduced, so that the device has a good heat dissipation effect, and the reliability is improved.

Description

Surface emitting laser

Technical Field

The utility model relates to a face penetrates the type laser instrument field, especially relates to a face penetrates type laser instrument.

Background

As a semiconductor for Emitting Laser light perpendicular to a top Surface, a Vertical-Cavity Surface-Emitting Laser (VCSEL) integrates the advantages of high output power, high conversion efficiency, high quality light beam, and the like, and has great advantages in precision, miniaturization, low power consumption, reliability, and the like compared with an LED and an edge-Emitting Laser, and thus receives great attention.

The limiting layer in the surface emitting laser plays a role in limiting carriers transversely, so that current flows from the P-type electrode, passes through the P-type DBR, flows through the current injection port of the limiting layer, flows into the resonance region and the N-type DBR, and finally reaches the N-type electrode. The commonly used VCSEL electrodes in the industry are mainly designed on the cap layer of the P-type DBR and the buffer layer of the N-type DBR, resulting in a longer conductive path and a wider oxide doping range of the confinement layer. In addition, since the surface emitting laser generally designs an electric field and an optical field in a GaAs structure, a certain load is imposed on chip heat generation and power consumption.

In view of the above, it is important to design a surface emitting laser that can optimize a conductive path and improve heat dissipation.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to overcome the not enough that prior art exists, provide a surface emitting laser.

In order to realize the above purpose, the technical scheme of the utility model is that:

a surface emitting laser comprises a substrate, an N-type DBR, a resonance area, a limiting layer and a P-type DBR, wherein the substrate, the N-type DBR, the resonance area, the limiting layer and an insulating area are arranged from bottom to top, the limiting layer comprises a current injection area and an insulating area, the current injection area is arranged in the middle of the current injection area, the insulating area is arranged on the periphery of the current injection area, the P-type DBR is formed by stacking a plurality of reflecting layers, the P-type DBR comprises a middle area and an outer ring area, the outer ring area is arranged above the current injection area of the limiting layer, the projection area of the outer ring area on the limiting layer is arranged in the insulating area of the limiting layer, at least part of the upper surfaces of at least one pair of reflecting layers at the bottom of the outer ring area is exposed, at least part of the upper surfaces of at least one pair of exposed reflecting layers is a low table top, the low table top is adjacent to the middle area, a P-type electrode is arranged on the outer ring area of the P-type DBR, and the P-type DBR at least covers the low table top.

Preferably, the projected area of the low mesa on the confinement layer is at least 50% of the projected area of the outer annular region on the confinement layer.

Preferably, a pair of reflective layers is disposed between the lower mesa and the confinement layer.

Preferably, the pair of reflection layers includes a high refractive index layer and a low refractive index layer which are stacked, and at least a part of an upper surface of the low refractive index layer of the at least one pair of reflection layers at the bottom of the outer ring region is exposed.

Preferably, passivation layers are arranged from two sides of the N-type DBR to the top of the P-type DBR except for the light emergent region and the low mesa.

Preferably, the low mesa is a part of an upper surface of at least one pair of reflective layers at the bottom of the exposed outer ring region, a high mesa which is located around the low mesa and flush with the top of the middle region is further disposed on the outer ring region, and the P-type electrode extends from the low mesa to the passivation layer of the high mesa and covers the passivation layer on the sidewall between the low mesa and the high mesa.

Preferably, a trench having the low mesa as a bottom surface is formed between the high mesa and the intermediate region.

Preferably, the depth ratio of the groove is greater than 1.

Preferably, the lower mesa is an entire upper surface of the at least one pair of reflective layers at the bottom of the outer ring region exposed, and the P-type electrode covers the lower mesa.

Preferably, the N-type electrode is provided on the substrate around the N-type DBR.

Compared with the prior art, the beneficial effects of the utility model are that:

(1) The surface emitting laser is optimized on a conducting path according to the design of a P-type electrode, the middle region is arranged on the P-type DBR to protect a light emitting region, the shading condition is avoided, the contact surface of the P-type electrode of the outer ring region of the P-type DBR is adjusted, and the conducting path and the current diffusion state are shortened.

(2) The surface emitting laser carries out different electrical property adjustments by changing the position of the P-type electrode, shortens a current diffusion path and improves the reliability of a device.

(3) The surface emitting laser can improve the stress condition in the oxidation process of the limiting layer, and utilizes the metal characteristic of the P-type electrode to realize a good heat dissipation effect.

Drawings

Fig. 1 is a schematic view of a surface emitting laser according to a first embodiment of the present application;

fig. 2 is a schematic diagram of a surface emitting laser according to a first embodiment of the present application;

reference numerals: 1. a substrate; 2. an N-type DBR; 3. a resonance region; 4. a confinement layer; 41. a current injection region; 42. an insulating region; 5. a P-type DBR; 51. a middle region; 52. an outer ring region; 521. a low table top; 522. a high table top; 6. an N-type electrode; 7. a P-type electrode; 8. and a passivation layer.

Detailed Description

The invention is further explained below with reference to the drawings and the specific embodiments. The drawings of the utility model are only schematic to facilitate understanding of the utility model, and the concrete proportion can be adjusted according to the design requirements. The definitions of the top and bottom relationships of the relative elements and the front and back sides of the figures described herein are understood by those skilled in the art to refer to the relative positions of the components and thus all of the components may be flipped to present the same components and still fall within the scope of the present disclosure.

Example one

Referring to fig. 1, an embodiment of the present application proposes a surface emitting laser including a substrate 1, an N-type DBR 2, a resonance region 3, a confinement layer 4, and a P-type DBR5, which are arranged from bottom to top, the P-type DBR5 and the N-type DBR 2 each being composed of AlGaAs and GaAs, and the substrate 1 being N-type GaAs. The P-type DBR5 is provided with a P-type electrode 7, the substrate 1 is provided with an N-type electrode 6, specifically, the substrate 1 around the N-type DBR 2 is provided with the N-type electrode 6, and the N-type electrode 6 is an annular metal ring surrounding the N-type DBR 2. The limiting layer 4 comprises a current injection region 41 positioned in the middle and an insulating region 42 positioned on the periphery, the current injection region 41 and the insulating region 42 of the limiting layer 4 are made by adopting an oxidation limiting process, the oxidation limiting process is an effective transverse limiting method, the process is simple, the thermal stability is good, the doping concentration can be independently controlled in the processing process, the uniformity is good, the method is suitable for large-area processing, and the yield is high. The P-type DBR5 is formed by stacking a plurality of reflective layers, one pair of reflective layers includes a high refractive index layer and a low refractive index layer which are stacked, and a plurality of pairs of reflective layers are stacked to form a distributed bragg reflector. Similarly, the N-type DBR 2 is also a distributed bragg mirror composed of a stack of several reflective layers. When a voltage is applied to the P-type electrode 7 and the N-type electrode 6, the resonant region 3 can generate light of a specific wavelength, and the light of the specific wavelength is reflected back and forth between the P-type DBR5 and the N-type DBR 2 above and below the resonant region 3, is repeatedly amplified, forms laser light, and is emitted from the light emitting region at the top of the P-type DBR 5.

In a specific embodiment, the P-type electrode 7 applies a voltage on the P-type electrode 7 and the N-type electrode 6, a current diffusion path starts from the P-type electrode 7, flows through the P-type DBR5 and the current injection region 41 of the confinement layer 4, passes through the resonant region 3, and finally, the current diffuses to the N-type electrode 6 through the N-type DBR 2 to form a loop. The P-type DBR5 includes an intermediate region 51 and an outer ring region 52 other than the intermediate region 51, and the intermediate region 51 is provided above the current injection region 41 of the confinement layer 4, as indicated by a region a in fig. 1. The projection region of the outer ring region 52 on the confinement layer 4 is located in the insulation region 42 of the confinement layer 4, the P-type DBR5 is divided into two parts by the middle region 51 and the outer ring region 52, the middle region 51 does not affect the normal light emission of the laser, the P-type electrode 7 is arranged on the outer ring region 52, and the position of the P-type electrode 7 can be changed on the outer ring region 52 to optimize the conducting path in the laser. A portion of the surfaces of the at least one pair of reflective layers at the bottom of the outer ring region 52 is exposed, and the exposed portion of the surfaces of the at least one pair of reflective layers has a lower mesa 521, the lower mesa 521 being adjacent to the middle region 51. The upper surface of the low refractive index layer of at least one pair of reflective layers at the bottom of the outer ring region 52 is exposed, and the upper surface of the exposed low refractive index layer of the reflective layers is a low mesa 521. Preferably, a pair of reflective layers is provided between the lower mesa 521 and the confinement layer 4, and the lower mesa 521 is provided on the pair of reflective layers above the confinement layer 4.

The outer ring area 52 is also provided with a raised mesa 522 located around the lower mesa 521 and flush with the top of the middle area 51. The partially reflective layer on the outer ring region 52 is etched and a trench is formed around the middle region 51, that is, a trench is formed between the high mesa 522 and the middle region 51, the low mesa 521 is a bottom surface of the trench, and the high mesa 522 is a top portion of a sidewall of the trench in the outer ring region 52. Preferably, the depth ratio of the trench is greater than 1. During the etching process of the outer ring region 52 of the P-type DBR5, the etching stop layer protection material can be InP or InGaP, and the etching mechanism is chemical etching, and the etching depth is controllable. The P-type electrode 7 covers at least the lower mesa 521, in particular, the P-type electrode 7 extends from the lower mesa 521 to the upper mesa 522 and covers the sidewall between the lower mesa 521 and the upper mesa 522, that is, the P-type electrode 7 covers the bottom and the outer sidewall of the trench and extends to the top of the outer sidewall. Specifically, the projected area of the low mesa 521 on the confinement layer 4 is at least 50% of the projected area of the outer annular region 52 on the confinement layer 4. The P-type electrode 7 completely covers the low mesa 521, so that the P-type electrode 7 can make good contact with the exposed part of the low refractive index layer at the bottom of the outer ring region 52, and further, the conductive path of the laser is changed, so that current flows from the bottom of the outer ring region 52 to the current injection region 41 of the confinement layer 4.

In a specific embodiment, passivation layers 8 are provided from both sides of the N-type DBR 2 to the top of the P-type DBR5 except for the light emitting region and the low mesa 521. A passivation layer 8 extends from the sidewall of the N-type DBR 2 up to a region outside the top light exit region of the P-type DBR5 and covers the sidewall of the trench, and a P-type electrode 7 extends from the lower mesa 521 to the passivation layer 8 of the upper mesa 522 and covers the passivation layer 8 of the sidewall between the lower mesa 521 and the upper mesa 522. The P-type electrode 7 is in contact with the reflective layer of the P-type DBR5 at the lower mesa 521, achieving good conductive connection. The conductive path of the laser is finally a current flow from the P-type electrode 7 through the low mesa 521 into the current injection region 41 and to the resonant region 3, the N-type DBR 2 to the N-type electrode 6.

In particular, the confinement layer 4 above the resonance region 3 is primarily responsible for lateral confinement of the carriers, and formation of the confinement layer 4 is primarily achieved by lateral penetration of the implanted ions, which collide with nuclei within the crystal and produce lateral diffusion beneath the mask. On the premise of ensuring that the current can be injected into the resonance region 3, the larger the lateral diffusion, i.e., the larger the high-resistance region, the smaller the area of the injected current, and the lower the threshold current. Therefore, by adjusting the position of the P-type electrode 7 and optimizing the conductive path, the doping range can be reduced. In addition, the current injection region 41 of the limiting layer 4 is oxidized to be in a compressive stress form, the outer ring region 52 is provided with a groove, the reflecting layer on the outer ring region 52 is thinned, the compressive stress can be effectively released, more energy can be converged to a light emitting end, and a current conduction path is improved, the inner diameter of the P-type electrode 7 and the size of the current injection region 41 are designed to have a tolerance, and the P-type electrode 7 is only arranged on the outer ring region 52, so that the shading condition of the top of the passivation layer 8 on the middle region 51 due to metal covering is not considered, and the P-type electrode 7 is made of metal, and the heat dissipation effect can be improved.

In a specific embodiment, taking an 850nm vcsel laser as an example, according to the thickness d = λ/4n, where λ is the wavelength, n is the refractive index, the total number of pairs of the reflective layers of the P-type DBR5 is 28-34 pairs, and the total thickness is 3.6-4.2 um. The outer ring region 52 of the P-type DBR5 is etched to a depth of 3.2-4.0 um to a pair of reflective layers above the confinement layer 4, i.e., the P-type DBR 5. Specifically, the total number of pairs of the reflective layers of the P-type DBR5 is 28 pairs, the total number of pairs of the reflective layers of the N-type DBR 2 is 33 pairs, the total thickness of the P-type DBR5 is 3.64um, the etching depth of the P-type DBR5 is 3.25um, and the distance between the two side walls of the trench is 3.5um.

Example two

The difference between the second embodiment and the first embodiment of the present application is: referring to fig. 2, the entire upper surfaces of the at least one pair of reflective layers at the bottom of the outer ring region 52 are exposed, the entire upper surfaces of the exposed at least one pair of reflective layers are the lower mesas 521, and the p-type electrodes 7 are covered on the lower mesas 521. That is, the P-type electrodes 7 are disposed on at least one pair of reflective layers at the bottom of the outer ring region 52. The structure can optimize the structural design of the P-type electrode 7, and can keep the performance of the original laser so as to achieve the chip characteristics of high speed or low junction temperature. The passivation layer 8 extends upward from the sidewall of the N-type DBR 2 to the outer wall of the outer ring region 52 of the P-type DBR5, and is disposed in the region outside the sidewall and the top light-emitting region of the outer ring region 52 of the P-type DBR5, and the passivation layer 8 is not disposed on the lower mesa 521, so as to ensure good conductivity between the P-type electrode 7 and the reflective layer. The N-type electrode 6 may be a ring-shaped metal ring having a gap around the N-type DBR 2, and preferably, the N-type electrode 6 may be a semi-ring-shaped metal ring. The rest is the same as in the first embodiment.

The above embodiments are only used to further illustrate the technical solution of the present invention, but the present invention is not limited to the embodiments, and any simple modification, equivalent change and modification made by the technical entity of the present invention to the above embodiments all fall into the protection scope of the technical solution of the present invention.

Claims

1. A surface-emitting laser characterized by: the optical waveguide grating comprises a substrate, an N-type DBR, a resonant region, a limiting layer and a P-type DBR, wherein the substrate, the N-type DBR, the resonant region, the limiting layer and an insulating region are arranged from bottom to top, the limiting layer comprises a current injection region and an insulating region, the current injection region is arranged in the middle of the current injection region, the insulating region is arranged on the periphery of the current injection region, the P-type DBR is formed by stacking a plurality of reflecting layers, the P-type DBR comprises a middle region and an outer ring region, the outer ring region is arranged above the current injection region of the limiting layer, the projection region of the outer ring region on the limiting layer is arranged in the insulating region of the limiting layer, at least part of the upper surfaces of at least one pair of reflecting layers at the bottom of the outer ring region is exposed, at least part of the upper surfaces of at least one pair of exposed reflecting layers is a low table top, the low table top is adjacent to the middle region, a P-type electrode is arranged on the outer ring region of the P-type DBR, and at least one P-type electrode covers the low table top.

2. The surface emitting laser according to claim 1, wherein: the projected area of the low mesa on the confinement layer is at least 50% of the projected area of the outer annular region on the confinement layer.

3. The surface emitting laser according to claim 1, wherein: a pair of reflecting layers is arranged between the low table-board and the limiting layer.

4. The surface emitting laser according to claim 1, wherein: the pair of reflection layers includes a high refractive index layer and a low refractive index layer which are stacked, and at least a part of the upper surface of the low refractive index layer of the at least one pair of reflection layers at the bottom of the outer ring region is exposed.

5. The surface emitting laser according to claim 1, wherein: and passivation layers are arranged from two sides of the N-type DBR to the top of the P-type DBR except for the light emergent area and the low mesa.

6. The surface emitting laser according to claim 5, wherein: the low mesa is the partial upper surface of at least a pair of reflection stratum of the bottom in the outer loop region that is exposed, still be equipped with on the outer loop region and lie in around the low mesa with the top of middle zone is leveled high mesa, the P type electrode extends to the passivation layer of high mesa from the low mesa and covers on the passivation layer of the lateral wall between low mesa and high mesa.

7. The surface emitting laser according to claim 6, wherein: and a groove with the low mesa as a bottom surface is formed between the high mesa and the middle region.

8. The surface emitting laser according to claim 7, wherein: the depth ratio of the groove is larger than 1.

9. The surface emitting laser according to claim 1, wherein: the lower mesa is the whole upper surface of at least one pair of reflective layers at the bottom of the outer ring region which is exposed, and the P-type electrode covers on the lower mesa.

10. The surface emitting laser according to claim 1, wherein: the substrate around the N-type DBR is provided with the N-type electrode.