GaAs_(0.6)P_(0.4):Te深中心的电声耦合与晶格弛豫

ELECTRON-PHONON COUPLE AND LATTICE-RELAXATION EFFECT OF DEEP CENTERS IN GaAs_(0.6)P_(0.4):Te

用DLTS技术结合光电容定态谱、瞬态谱、OITS谱研究了GaAs_(0.6)P_(0.4):Te深中心的光电性质和电声耦合作用,在GaAs_(0.6)P_(0.4):Te中检测到两种深中心(A和B中心),表观热激活能分别为0.20和0.40eV,光离化阀值分别为0.60和1.31eV。详细研究了B中心的特性,测量了光离化截面谱的温度关系,发现有明显的声于展宽现象和晶格弛豫效应,并在低温(90K)观察到B中心的持续光电导效应。描绘出位形坐标图,说明了实验结果,较好地描述了B中心的特性,确认B中心属于DX中心。

GaAs0.6P0.4:Te is an important photo-electronic material. Recently increasing altension has been paid to the deep centeis in it. But the studies on the complex properties and microscopic structures of these deep centers are not efficient. In this paper we report the results of deep centers in GaAs0.8P0.4:Te studied by DLTS, steady and transient photo-capacitance, OITS and initial slope method. The photo-electronic properties and eleclron-phonon couple effects of the deep centers have been analyzed.In the samples we delected two kinds of deep center named center A and center B. With DLTS technique we got their apparent thermal activation energies: EcA=0.20eV and EeB=0.40eV. With steady photo-capacitance technique we got their photoionization threshold energies. EA0=0.6cV and EB0=1.3eV. Both of the centers have large difference between apparent thermal activation energy and photoionzation threshold energy, which shows that center A and B have large lattice relaxation effect (strong electron-phonon couple effect).Our analyses with steady photo-capacitance and OITS technique show that the capacitance transient resulting from the homogeneous detecting light with energy over 1.2eV may be thought as the result of the carrier transition of center B. So v e can use initial slope method to get the optical ionizalion cross section spectra.We studied the relation of the optical ionization cross section spectra of center B to the temperature. At 104K,148K and 197K we measured the optical ionization cross section spectra of center B. It is sho n that center B has obvi-ous phonon-broaden effect-the optical ionization cross section spoctrum drifts towards lower photon energy and broadens.To our kno ledge this result has never been reported. The phonon-broaden effect shows that center B has large lattice relaxation effect.We fit the optical ionizalion cross section with the Lucovsky model, getting the photoionization threshold energy of center B EB0=1.31eV,which is consistent with the result of steady transient capacitance spectra.According to Huang Kun's electron-phonon couple theory we draw a configuration coordinate diagram to describe the photo-electronic properties of center B.At low temperature (90K) we have observed the persistent photoconduclion effect (PPC) of center B which is the v onderful property of DX center.These results suggest that center B in GaAs0.6P0.4 :Te belong to DX center.