Structure Research Of Current Injected GaN-based Semiconductor Lasers

GaN-based semiconductor lasers(LDs)have attracted considerable attention because of their important applications in such fields as high-density optical storage,sterilization,laser display and chemical/biochemical analysis.To improve the performance of GaN-based LDs,a great deal of research work has been launched into structure designs and output characteristics of LDs.Optimizing and numerical simulating the LDs' structure by using the existing theory of semiconductor,can shorten the research time and improve the efficiency of investigation.This thesis studies current injected GaN-based semiconductor lasers by PICS3D software,including edge-emitting Laser(EEL),vertical cavity surface emitting laser(VCSEL).The main contents are as follows:1)This thesis introduced the material properties of ? nitride,the development current situation,work principle and challenging issues of GaN-based semiconductor lasers.Besides,the operational processes of PICS3D software and some basic physical models involved in the simulation are provided.2)A brief introduction to the basic structure,performance characteristics and research progress of GaN-based edge-emitting laser was made.Conventional current injected AlGaN-based ultraviolet EELs and EELs with step-graded quantum barriers(QBs)were built by using the software PICS3D.Through the calculation and comparative analysis of these two kinds of structure,it is found that the structure with step-graded QBs exhibits higher output light power,slope efficiency and emission intensity,as well as lower series resistance and threshold current density under the identical condition,compared with conventional LD structure.The performances are greatly enhanced in laser diodes with step-graded QBs.Though there have been a number of studies on structure optimization of GaN-based edge-emitting laser by the commercial software PICS3D,the researches on AlGaN UV-LD by PICS3D are rarely seen,and we hope this report will motivate further research in the area of AlGaN UV-LDs.3)The basic structure and research development of GaN-based vertical cavity surface emitting laser,as well as the difference between VCSEL and EEL were introduced in the thesis.We investigated the effects of cavity length on the output performances of current-injected GaN-based vertical cavity surface emitting lasers by using the software PICS3D.The results indicated that with diminishing the cavity length to some extent,the threshold current was decreased,the slope efficiency was enhanced,and the output performances of VCSELs were promoted.However,the cavity length should not be too short because of the complexity of device growth and structure.It is important to understand the influence of the length on the VCSELs,which has great guiding significance for the structure design and performance studies.