显微光谱研究半绝缘GaAs带边以上E_0+Δ_0光学性质

Optical properties of the E_0+Δ_0 energy level higher than the bandgap of GaAs studied by micro-photoluminescence technique

通过显微光致发光技术和显微拉曼(Raman)技术研究了半绝缘GaAs(SI-GaAs)晶体的带边附近的发光.在光荧光谱中,观察到在高于GaAs带边0.348eV处有一个新的荧光峰.结合Raman谱指认此发光峰来源于GaAs的E0+Δ0能级的非平衡荧光发射.同时,通过研究E0+Δ0能级的偏振、激发光强度依赖关系,以及温度依赖关系说明E0+Δ0能级与带边E0共享了共同的导带位置Γ6,同时这也说明在GaAs中主要是导带的性质决定了材料的光学行为.同时,通过与n-GaAs和δ掺杂GaAs相比较,半绝缘GaAs晶体的E0+Δ0能级的发光峰更能反映GaAs电子能级高临界点E0+Δ0的能量位置和物理性质.研究结果说明显微光致发光技术是研究半导体材料带边以上能级光学性质的一种非常有力的研究工具.

Using micro-photoluminescence technique, we observed a new photoluminescence peak about 0. 348 eV above the bandgap of GaAs （ Eo ） . By analyzing its optical characteristics, we assigned this peak to the nonequilibrium luminescence emission from theEo ＋ △o bandgap in semi-insulated GaAs, which was further verified by Raman results. The observed polarization, excitation power dependence and temperature dependence of the photoluminescence spectra from the Eo ＋ △o energy level were very similar to those from the Eo of GaAs. This mainly resulted from the common conduction band around Г6 that was involved in the two optical transition processes, and indicated that the optical properties of bulk GaAs were mainly determined by the intrinsic properties of the conduction band. Our results demonstrated that the micro-photoluminescence technique is a powerful tool to investigate the high energy states above the fundamental bandgap in semiconductor materials.