Photoluminescence Study On Bandedge Electronic Structure Of CdZnTe And Interfacial Properties Of InGaAs(N,Bi)/GaAs

As the foundation and precursor of optoelectronic science and technology,optoelectronic materials are a key theme in scientific research.Semiconductors have been investigated for optoelectronic applications for decades and playing important roles in the areas of information,transportation,energy,medicine and military.Cd_1-xZn_xTe crystal is widely used for photoelectric detection because of the Zn composition-dependent photoelectric properties,it can be used for room-temperature nuclear detector with x=0.05⁰.4 and as substrate of long-wavelength HgCdTe epilayer with x=0.04.Dilute-nitride?dilute-N?and–bismide?dilute-Bi?III-V semiconductors have attracted great interests and are expected to be important for near infrared laser diodes because of the advantages in band engineering.While the development of materials and devices is fast,however,the mechanisms are to be resolved of defects and their effects on optoelectronic properties in CdZnTe,and dilute-N/Bi effects on the interfacial properties in InGaAs quantum wells?QWs?.It is crucial to analyze the nature of the defects and their correlation with doping/annealing for further optimization of CdZnTe,and the interfacial properties and their evolution with annealing in dilute-N/Bi InGaAs QWs for improved optoelectronic performance.As a convenient and nondestructive optical spectroscopic technique,photoluminescence?PL?has been widely used in the study of semiconductor band structures and optoelectronic properties.The Fourier transform infrared?FTIR?spectrometer-based PL method manifests advantages of high flux and high sensitivity,and shows technical superiority in the study of semiconductor defects,with combination of optimized sensitivity and condition-variable capability.Based on a continuous-scanning FTIR-PL method and variable conditions of temperature,excitation and magnetic field,we in this work investigate the electronic structures and defect behaviors of Cd ZnTe,InGaAsN/GaAs and InGaAsBi/GaAs QWs,with special focus on the defects evolution with various annealing conditions.The key results and progresses are as follows:1..Mechanisms of shallow levels are clarified for CdZnTe samples with specific components by temperature-,power-,magnetic field-and spatial-dependent PL analyses.Tensile strain is also evidenced,which results in the up-shift of the light-hole valenceband.2.New characteristic SA recombination is clarified,and the mechanisms and evolution with annealing of A-center and SA recombination are investigated by low-temperature PL analysis of CdZn Te with different growth and annealing conditions.Depth-dependent distributions of impurities and defects in CdZnTe are characterized by etching and scanning electron microscopy.A model is proposed for the annealing effects,and electronic band structure is established for the CdZnTe.3.By temperature-,power-,and magnetic field-dependent PL analyses,it is revealed that?i?annealing reduces In cluster-induced content nonuniform and/or well-width fluctuation in InGaAs/GaAs and InGaAsN/GaAs QWs as it drives In-Ga interdiffusion across the interfaces and improves the interfacial crystal quality,?ii?In-Ga interdiffusion is not enhanced significantly by N incorporation with 1.2%N content,while the exciton binding energy gets enhanced and the interfacial content nonuniform aggravated.4.The electronic structures of In GaAsBi/GaAs and InGaAs/GaAs QWs are analyzed by temperature-,power-and magnetic field-dependent PL measurements.Spectral fittings indicate that?i?besides the thickness fluctuation,localized states exist near the interface of InGaAs/GaAs quantum well;?ii?Bi may weaken the interfacial lattice mismatch,eliminate In segregation,reduce band structure fluctuation,lower Auger recombination,and hence improve the optoelectronic performance.