FRANZ-KELDYSH OSCILLATION FROM THE SPACE CHARGE REGION OF MBE GaAs FILMS

We have investigated doped MBE GaAs films using photoreflectance (PR) spec-troscopy. Special spectral structures have been observed in the vicinity of the funda-mental band gap, which are quite different from the Franz-Keldysh oscillation (FKO) from uniform electric fields under flatband modulations. Numerical analysis has been performed for FKO from electric fields in the space charge region under non-flatband modulations. Some typical FKO line shapes are illustrated. For moderately doped samples the calculated line shapes are basically consistent with experiments. The surface electric field and the Fermi level pinning have also been deduced from exper-iments.     

掺杂分子束外延GaAs薄膜表面和GaAs-GaAs界面的光反射调制谱

报道了用光反射调制谱(PR)测量掺杂分子束外延GaAs薄膜表面和界面电场的结果。分别用He-Ne激光和He-Cd激光作调制光,由于它们的穿透深度不同,可以有效地区分来自表面和界面的PR信号。由PR谱推算出薄膜表面和界面的电场。研究了薄膜干涉效应对调制光谱的影响,对界面电场的成因进行了分析和讨论。 关键词：