Structural Optimization Of Group Ⅲ Nitride Semiconductor Deep Ultraviolet Laser Diode

Semiconductor laser diodes have covered a wide range of wavelengths from terahertz to ultraviolet.They have very important applications in many fields,such as industry,transportation,communication,information processing,health care,culture and education.The purpose of this thesis is to optimize the performance of deep ultraviolet laser diode(DUV-LD)designed with group III nitride semiconductor materials.Because the laser diode with group III nitride materials has a relatively large band gap that can directly contain blue light,green light,purple light and ultraviolet light,and its luminous characteristics are far better than other materials in the past.The characteristics of these materials determine the inevitability that group III nitride materials can be used to make optical devices.The electron barrier layer(EBL),waveguide layer(WGL)and active region structure of deep UV laser diode are optimized by using Crosslight’s lastip simulation software.In order to solve the problems of high electron leakage,hole leakage and low carrier recombination rate,the simulation experiment of DUV-LD optimization is carried out.The main contents of this thesis as follows:1.For DUV-LD with lasing wavelength less than 280 nm,one of the severe problems is the problem of electron leakage.At present,the common method is to add an Al GaN electron barrier layer(EBL)structure into the p-type.This EBL structure can provide an additional potential barrier in the p-type layer,which can effectively prevent electrons from overflowing from the active region to the p-type,so as to reduce the problem of electron leakage and effectively improve the performance of Al GaN based deep UV laser diode.The deep UV laser diodes with rectangular EBL,positive ladder rectangular EBL and inverted ladder rectangular EBL are compared and studied.The experimental results show that the DUV-LD with inverted ladder rectangular electron barrier structure can provide higher electron effective barrier and effectively suppress electron leakage.2.In order to make photons gather in the active region of DUV-LD efficiently,the upper and lower waveguide layer(WGL)structure is optimized in the DUV-LD structure,and Al GaN material with lower refractive index than the active region is selected.Because the refractive index of photons in the upper and lower waveguide layers is lower than that in the active region,the light can be better limited in the active region,so that the DUV-LD can obtain higher optical gain.Therefore,the photoelectric performance of DUV-LD can be effectively improved by optimizing the upper and lower waveguide layers.The DUV-LD with rectangular WGL,single step WGL and double step WGL structures are compared and studied.It is concluded that the DUVLD with new double step upper waveguide layer and double step lower waveguide layer can not only improve the material gain of the device,but also provide higher electron effective barrier at the upper waveguide layer and higher hole effective barrier at the lower waveguide layer,Thus,the problems of electron leakage and hole leakage are effectively restrained.3.A BGaN based deep ultraviolet laser diode with a lasing wavelength of 267 nm is proposed.The simulation focuses on the design and optimization of the active region structure of BGaN based deep UV laser diode,including the optimization of the number of layers of quantum wells in the active region and the thickness of quantum wells(QW)and quantum barrier(QB).After improvement,a high-performance device with a threshold current of 23.68 m A and an output power of 129 m W can be obtained when the injection current is 80 m A.The optimization scheme of the structure of deep ultraviolet laser diode mentioned in this thesis is of great significance to improve the problems of electron leakage,hole leakage and low carrier recombination rate.