Investigations On Structure Optimization Of P-type Layer And Active Region Of AlGaN-Based Ultraviolet Laser Diodes

Ultraviolet laser diodes(UV-LDs)has been widely used in biological detection,medical diagnosis,chemical analysis,disinfection,sterilization and high density data storage.Semiconductor UV-LDs.have the advantages of high quality and efficiency while low cost and small volume compared with others such as solid or gas lasers.Furthermore,the Ⅲ nitride material-AlGaN has a continuously adjustable band gap and excellent physical properties including high electron mobility,high thermal conductivity,high temperature resistance,corrosion resistance,etc,,which is a good alternate for preparing semiconductor UV-LDs.However,there are still many challenges in AlGaN-based UV-LDs,such as poor material quality,strong spontaneous polarization effects,low effective carrier injection,difficulties in p-doping and so on.Many researchers have devoted themselves to the performance improvement and related mechanism of AlGaN-based UV-LDs.Simulation about optoelectronic devices in terms of existing theories can greatly shorten the research time and upgrade the efficiency.In this paper,PICS3D software is used to simulate electrically pumped AlGaN-based semiconductor UV-LDs,in order to obtain new structures with better performance containing two parts.The first is to modify the p-type injection layer,we use a superlattice structure to replace the origin bulk layer,the other proposes a stepped quantum barrier UV-LDs summarized as follow:1)The development,principles,characteristics of semiconductor laser diodes and the properties of Ⅲ nitride materials are introduced.In addition,the current research progress and main problems of semiconductor UV-LDs are summarized.Then the operation of the semiconductor devices simulation software PICS3D and the theoretical basis of calculations are introduced too.2)PICS3D software is used to simulate UV-LDs referring to an experiment sample in related literatures.Novel superlattice p-tpye layer is investigated.By comparing different structure with varied Al composition superlattices,the sample with a superlattice structure consisting of 5 nm p-doping Al0.25Ga0.75N and 5 nm undoped Al0.20Ga0.80N shows the best capability,which owns better carrier confinement,higher optical output power,higher carrier injection,higher stimulated recombination rate,lower threshold current and lower electron leakage,realizing the performance improvement of UV-LDs.3)PICS3D is used to explore the active region of AlGaN-based UV-LDs.The number of quantum wells is studied firstly.Then,the influence of the stepped quantum barrier on the device performance is explored.The results show that replacing the 12 nm Al0.16Ga0.84N barriers with 6 nm Al0.16Ga0.84N and 6 nm Al0.12Ga0.88N stepped quantum barriers can improve the luminous efficiency of the device.The band structure,carrier density,carrier recombination,etc.are analyzed.