Study of Wannier-Stark Effect in GaAs/AlGaAs Superlattices

为了澄清Di Carlo等人所预测的“Wannier-Stark共振”现象的存在，我们在本征层测量了具有（GaAs） _5/ (AlAs) _2超晶格的引脚二极管的齐纳电流。我们使用的样本是由慕尼黑工业大学的魏曼教授小组培养的。我们采用标准锁相技术测量了齐纳电流的导数信号，并在齐纳电流的二阶导数中观察到几个峰值。峰值位置与理论值吻合较好。为了阐明超晶格的电子能带结构，还进行了电反射测量。观察到的电反射光谱清楚地显示了超晶格中斯塔克阶梯的形成。斯塔克阶梯的能量与齐纳电流二阶导数的峰值电压有很好的对应关系。这些结果有力地表明，齐纳电流二阶导数中的峰是由超晶格中的斯塔克阶梯产生的。总之，我们找到了wanner - stark共振的实验证据。

In order to clarify the existense of a new phenomenon called "Wannier-Stark resonance" which was predicted by Di Carlo et al., we measured Zener current throught a pin diode with a (GaAs) _5/ (AlAs) _2 superlattice in the intrinsic layr. The sample we used were grown by the group of professor Weimann in Munchen Institute of Technology. We measured the derivative signals of Zener current by employing a standard lock-in technique and observed several peaks in the second derivative of Zener current. The peak positions agree well with theoretical values. Electroreflectance measurements were also carried out so as to clarify electronic band structure of the superlattice. Observed electroreflectance spectra clearly show the formation of Stark-ladders in the superlattice. Energies of the Stark-ladders show good correspondence to the peak voltages of the second derivative of the Zener current. These results strongly indicates that the peaks in the second derivative of Zener current arise from Stark-ladders in the superlattice.In conclusion, we found an experimental evidence for the Wannier-Stark resonances.