Study On Photoluminescence Spectra Of Band-edge Electronic Structure Of GaAsBi Semiconductor

As a powerful method for semiconductor research,photoluminescence has been widely used in studing for the photoelectric properties of semiconductor,such as the band gap,band-edge levels and band-tail states,base on its advantages of non-contact and high sensitivity.The Fourier Transform Infrared(FTIR)spectrometer-based PL method makes full use of the FTIR spectrometer's multi-channel,high-throughput advantages,thereby significantly improving the signal-to-noise ratio(SNR)and spectral resolution.It provides an effective means for the acquisition and quantitative analysis of weak signals.Ga As Bi semiconductor has attracted much attention in the world due to strong application potential in infrared optoelectronic devices,base on its large Bi-induced bandgap reduction,low temperature sensitivity and ability of suppressing the Auger recombination.In order to improve the amount of Bi content,the molecular beam epitaxial growth temperature of Ga As Bi is usually lower than that of Ga As.Thus,intricate localized levels and band-tail states may be introduced during the growth process which limits the optoelectronic properties of dilute semiconductor.Therefore,it is important to clarify the influence of the local levels/band-tail states of Ga As Bi on its electronic structure,both for the mechanism understanding of materials and for the application of photoelectric characteristics.In this work,the spectral quality is optimized by solving the technical problem of low PL SNR for band-tail states-related PL spectra under the extremely weak power.Based on the FTIR-PL method,exploring the excitation power-and magnetic fieldand temperature-dependent PL measurements of Ga As1-x Bix.It includes the following three parts:(i)Aiming at low SNR of weak power PL on the Ga As1-x Bix band-tail levels,spot size-dependent PL test was performed on two Ga As1-x Bix samples.The results show: when the excitation power remains unchanged,PL shift red with spot size,which is due to the decrease of the equivalent power density;when the excitation power density is kept constant,the PL lineshape is unchanged.However,SNR of the PL is improved as the spot size rise,which is beneficial to the quantitative fitting analysis of the spectra.(ii)The Ga As1-x Bix band-edge levels are studied by multivariable conditional PL.Base on the analysis of power-dependent PL,found that:(1)The PL spectra are asymmetrical at different excitations;The three features fitted by the Gauss-Lorentz curve are blue-shifted with power;(2)The linear relationship between the PL intensity of three features and power at low level excludes the possibility of free-exciton recombination;(3)The evolution of FWHM with power indicates that the blue shift of PL is due to carrier filling in band-tail states rather than Donor-acceptor pair recombination;(4)In addition,it is found that Bi content has a effect on the density of states of Ga As1-x Bix;In the magnetic field-dependent PL study,The invariance of the PL linear shape with magnetic field further ruled out the possibility of participation of the conduction band;Different Bi-induced bandgap reduction reported in literatures are explained in this work.In addition,the temperature-dependent PL evolution of Ga As1-x Bx was studied,the result confirmed the effect of Bi content on temperature sensitivity of Ga As1-x Bix;The result of the temperature-dependent transmission spectra are consistent with the above conclusions.(iii)Exploring the PL evolution of QDs when Ga As1-x Bix is used as the strain buffer layer of In As QDs.Preliminary results show that the PL of In As QDs is red/blue shift with the increase of Bi content/thickness of SBL/SRL of Ga As1-x Bix.The red/blue shift is due to the effects of strain and barrier height.