Nitride semiconductor vertical cavity surface emitting laser, and manufacturing method and application thereof

Abstract

The invention discloses a nitride semiconductor vertical cavity surface emitting laser, and a manufacturing method and application thereof. The nitride semiconductor vertical cavity surface emitting laser (VCSEL) comprises an n-side DBR structure, an active region and a p-side DBR structure which are sequentially arranged in the preset direction, and a current limiting structure is formed on the n side of the laser. Furthermore, the p side of the laser is bonded with a supporting sheet. The nitride semiconductor vertical cavity surface emitting laser provided by the invention has the advantages of low device resistance, small working voltage, low thermal resistance, good heat dissipation effect, low junction temperature, simple process and the like, the performance of the nitride semiconductor VCSEL can be greatly enhanced, the service life of the nitride semiconductor VCSEL can be greatly prolonged, and the working stability of the laser is improved.

Description

technical field [0001] The invention relates to a vertical-cavity surface-emitting laser (Vertical-Cavity Surface-Emitting Laser, VCSEL), in particular to a nitride semiconductor vertical-cavity surface-emitting laser, its manufacturing method and application, and belongs to the field of semiconductor photoelectric technology. Background technique [0002] Group III nitride semiconductor materials represented by gallium nitride (GaN) have excellent characteristics such as large band gap, direct band gap, high temperature resistance, and radiation resistance. The band gap covers the spectral range from deep ultraviolet to near infrared. It has important application value and can be used to prepare high-efficiency light-emitting diodes, semiconductor lasers and the like. Group III nitride semiconductor lasers are an important part of trichromatic laser light sources and the core components of a new generation of laser display technology, and have very broad application prospec...

AI Technical Summary

Problems solved by technology

The laser emission direction of the edge-emitting laser is parallel to the surface of the chip, and its advantage is that the output power is relatively large; the disadvantages are: 1) Fast on-chip testing cannot be performed, and it needs to be tested after cleaving the epitaxial wafer to form a resonant cavity. The process is complicated, resulting in high R&D costs ; 2) The beam divergence angle is large, the near field and far field are elliptical distribution, and the coupling efficiency with the fiber is low; 3) Since the laser emission direction is parallel to the chip surface, it is difficult to realize a two-dimensional array

This structure VCSEL faces the following two main problems: 1) The light output aperture of this structure VCSEL usually does not exceed 10 μm, and the current needs to flow into the p-type layer through ITO with an aperture size of 10 μm. The contact area of ​​the p-side electrode is small and the contact resistance is high.

In addition, due to the hole concentration n(~10 17 cm -3 ) than the n-type electron concentration (10 18 ~10 19 cm -3 ) is 1 to 2 orders of magnitude lower, and the hole mobility μ (2 / V·s) than electrons (500~1000cm 2 / V s) is 1 to 2 orders of magnitude lower, which leads to a high resistivity (ρ=1 / n μ q) of the p-type hole injection region; combined with the hole injection area S (diameter ~ 10 μm) compared The n-side electron injection area (typically 200μm×200μm) is much smaller, so the p-side series resistance (R=ρ·L / S) of this structure VCSEL is huge

The higher p-side resistance leads to a high operating voltage of the device, resulting in a large thermal power, and the huge Joule heat generated leads to an increase in the junction temperature of the laser, which seriously affects the performance and reliability of the VCSEL.

2) Using dielectric films such as SiO2 or SiNx with low thermal conductivity as the current confinement layer will significantly increase the thermal resistance of the device, reduce the heat conduction inside the laser, and make the device dissipate heat It is more difficult and the thermal resistance is larger, which intensifies the thermal effect, causes the junction temperature of the device to rise, the non-radiative recombination of the active area is enhanced, the output power is reduced, and the life of the final device is greatly reduced, which seriously restricts the wide application of nitride semiconductor VCSEL.

However, this method does not solve the problem from the fundamental heat source: 1) This method still uses the traditional VCSEL structure, and still faces the above-mentioned problems of large series resistance and large thermal power on the p-side, and cannot reduce the Joule heat generation of the device

2) This method does not change the distance from the heat source (p-side nitride and active region) to the heat sink, and the heat transfer path is not shortened

3) The thickness of the insulating dielectric material in the device is usually only about 100 nanometers. Compared with the material with a thickness of nearly 100 microns from the heat source to the heat sink, this method of only improving the thermal conductivity of the insulating medium has a very limited effect on improving the overall thermal resistance of the device

This method actually exposes many problems: 1) Quantum well luminescence is very sensitive to defects, and etching will introduce a large amount of etching damage, and the quantum well sidewall damage after etching is difficult to repair, resulting in quantum well non-radiative Recombination enhancement, the quantum efficiency of the device is significantly reduced, and the threshold of the laser is therefore increased sharply

2) A large amount of etching damage will increase the leakage of the device, and reduce the life and reliability of the device

However, the hole injection area S on the p-side is significantly reduced from the usual 10 μm pore size to ~100 nm (depending on the number of quantum well pairs), which is reduced by nearly 1 to 2 orders of magnitude, which instead leads to a series resistance on the p-side (R = ρ·L / S) increase

4) The p-type layer in lateral contact with the quantum well needs to be prepared by lateral epitaxial growth above the DBR dielectric film below, and the diffusion and contamination of impurities such as Si and O in the dielectric film will also affect the electrical properties of the p-type material. and quantum well luminescence negatively affects

[0007] It can be found that the existing methods for reducing the resistance and thermal resistance of nitride semiconductor VCSEL generally have the following significant shortcomings: 1) seldom start from the fundamental VCSEL heat source, It is impossible to reduce the thermal resistance and resistance of the nitride semiconductor VCSEL at the same time; 2) It may cause unnecessary damage to the quantum well active area, reduce the quantum efficiency of the active area, increase the laser threshold, and cause device leakage, reducing device reliability 3) Growth / process complexity increases, device stability is poor, and practicability is poor

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