GaAs/Ga_xAl_(1-x)As异质结的调制反射光谱研究

STUDY OF PHOTOREFLECTANCE SPECTROSCOPY ON GaAs/GaAlAs HETEROJUNCTION

用光调制光谱方法研究了逐层腐蚀的GaAs/Ga_(1-x)Al_xAs异质结,发现不同厚度的GaAs复盖层对异质结表面层电子能带有很大影响,由GaAs带间跃迁的Franz-Keldysh效应计算出表面层表面电场随外延层的变薄而增大,并计算出表面费密能级与导带底的距离f=0.27(0.03)eV,通过对Ga_(1-x)Al_xAs调制光谱的分析,发现表面复盖层对Ga_(1-x)Al_xAs层的调制光谱线形有调节作用,不同厚度的复盖层使PR线形发失变化,这与考虑干涉效应后的理论预计线形一致。

The GaAs/GaAlAs heterojunctions with different thicknesses of cap layer were investigated by the use of photoreflectance (PR) spectroscopy. By analyzing the Franz-Keldysh Oscillation (FKO) in PR spectrum, it was found that the thickness of cap layer would influence the surface band structure of heterojunction, and the surface field was increased with the decrease of thickness of cap layer. It was also found that the PR lineshape would rotate with the varying of the thickness of cap layer. This is coincident with the theoretical calculation while considering the interference effect between different layers.