摘要
在77—300K温度范围内,用N_2分子激光器的3371谱线激发未故意掺杂的p型ZnTe晶体,得到了与自由激子有关的发射。发现随着激发密度的增加,其发光光谱的峰值位置红移而谱带的半宽度展宽,这些结果可以用E_x—e和E_x—E_x的相互作用来解释。
Luminescence of ZnTe crystal in the near band edge region has been investigated at 77K.Several explanations on the origin of near band edge emission have been reported. Cingolana et al. considered the origin as band -gap shrinkage appeared under high excitation density, Jin et al. considered it as bound-free transition,and Panowicz et al. considered it as ex-citon-carrier scattering.In present work, crystals of undoped p-ZnTe were grown by Bridgman method and photoluminescence spectra were measured by Model 44W spectrometer with RCA-C31034 photomultiplier under excitation of 3371A line of a N2 laser at 77-300K.The photoluminescence spectra of the ZnTe crystal under different excitation density at 77K are shown in Fig. 1 .The spectra under lower excitation density consist of three bands peaked at 5252A(E),5336A(FB0)and 5394 A (FB1)respectively. With increasing excitation density the width of E band becomes large and its peak position shifts towards longer wavelength, but the peak positions of FB0 and FB1 bands do not change. The FB0 and FB1 bands correspond to free-to-bound transition and its replica associated with 1 LO phonon, respectively. The E band is caused by exciton-carrier interactions.Fig.2 showes the dependence of the peak positions of E band under different excitation density on temperature in the range of 77-300K. With increasing excitation density, the dependence of peak position of E band on temperature in the range of 77-90K is quite different. When the excitation density I0 equals to 4MW/cm2, it nearly keeps no changing. This fact illu-strates that the composition of E band has already changed. Comparing the experiment of E band as shown in Fig. 3 at 77K with the theoretical result calculated by computer, it is found that the E band is composed by E'and P bands, the E' band might be contributed to the exciton-carrier scattering, and the P band to the exciton-exciton scattering.Collins et al.in PbI2have also worked out similar analysis. In the range of 90-300K,the behavior of E band shown in Fig. 2 indicates that exciton-carrier scattering plays a dominant role. Comparing photoluminescence spectra under different excitation density at 77K in Fig.1 with that at RT in Fig.4 we found that both E band at 77K and E band at RT have similar characters. This result indicates that the exciton-carrier scattering continues from 77K to RT.Because the peak position of FB0 transition is independent of the excitation density, we consider the shift towards olower energy of E band is caused by the exciton scattering,and is not due to the increasing of temperature of crystal lattice.As above discussion, we suggest that luminescence of the ZnTe crystal in the near band edge at RT might be attributed to the recombination of free exciton scattered by fres carrier.
出处
《发光学报》
EI
CAS
CSCD
北大核心
1989年第2期117-122,共6页
Chinese Journal of Luminescence
基金
国家自然科学基金
