摘要
采用有限深对称方势阱近似模型求解薛定谔方程得到Ge/Si量子阱中的子能级分布,并基于迭代法数值求解泊松方程模拟计算了量子阱结构样品在不同偏压下的载流子浓度分布和C-V特性.C-V曲线上电容平台的存在是量子阱结构C-V特性的显著特征,它与量子阱结构参数有密切的关系.随着覆盖层厚度的减小,C-V曲线上平台起始点的电容值增加,并且向低电压方向移动直至其消失.随着量子阱中的掺杂浓度提高,阱中的载流子浓度也会相应增加,那就需要更高的外加电压才能耗尽阱中的载流子,因此平台宽度也就随着掺杂浓度的增加而增加.当覆盖层厚度增加时,由于电压的分压作用,使得降在量子阱上的分压相应减少,因此需要更大的外加偏压才能使阱中载流子浓度全部耗尽,这就使平台的宽度增大.同样地,当覆盖层掺杂浓度增加时,覆盖层中更多的载流子转移到阱内,也就需要更高的外加偏压才能使阱中载流子全部耗尽,平台的宽度也就随之增大.
The energy levels of a Ge/Si quantum well were obtained by solving the Schoerdinger equation based on the finite potential well approximation. For the quantum well structure,the characteristics of capacitance-voltage （C-V） and the distribution of carrier concentration were derived in different bias voltage regions by analytically solving Poisson＇s equation. The appearance of a capacitance platform is a distinct characteristic of the C-V curve for quantum well structures,which is relative to the structure parameter of the quantum well. As the thickness of capping layer decreases, the starting capacitance of the C-V platform increases and shifts toward low reverse bias. As the doping concentration in the quantum well or the capping layer increases,a high reverse bias is needed to exhaust the carriers in the quantum well, and the platform width increases. The apparent carrier concentration distribution in the quantum well can be obtained from the C-V curve.
