权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Investigation of Photo-Response in Micro-structure Device of Photo-conducting Semiconductor and Superconductor

光电导半导体和超导体微结构器件的光响应研究

基本信息

批准号：
03452040
负责人：
TAKAOKA Sadao
金额：
$ 4.16万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1991
资助国家：
日本
起止时间：
1991 至 1993
项目状态：
已结题

项目摘要

In order to investigate the influence of illumination on the superconductivity proximity effect between superconductor and photo-conducting semiconductor, we have made the mesoscopic devices from a pair of Pb, In, Au multi-layr superconducting films on indium doped Pb_<1-x>Sn_xTe (x=0.25) semiconductor single crystal. The electron mobility is very high and the amount of persistent photoconductivity is large in indium doped Pb_<1-x>Sn_xTe, which indicates that the penetration length of superconductivity into semiconductor is long and could be varied widely. We measured the superconducting characteristic of these devices under illumination. In the devices with the gap width between the superconductor films below 0.2-0.3mum, the hysteresis in the current-voltage curve is observed at 4.2K, which is a typical characteristic of Josephson junction. Further the critical current (the sudden increase point of resistance) increases with increaseing illumination. From these results, we succeed in changing the superconducting characteristic of the mesoscopic device by illumination.Using an AC resistance bridge, which was purchased by this grant, we have also measured magnetic field dependence of capacitance in a two dimensional electron system (GaAs/AlGaAs heterostructure) in the quantum Hall regime. It has been found that the bottom values of capacitance at the Hall plateaus are determined not by the gate area but by the edge length of the gate. These results can not be explained by the conventional interpretation of magnetocapacitance, where the capacitance is directly related to the density of states of a two dimensional electron gas. We suggest a model that the bottom values are determined by the area of edge states. From this model, the widths of edge states were estimated and compared with the recent theory.

为了研究光照对超导体与光导半导体之间超导邻近效应的影响，我们在掺铟的Pb_<1-x>Sn_xTe（x=0.25）半导体单晶上采用一对Pb、In、Au多层超导薄膜制作了介观器件。掺铟Pb_1-xSn_xTe的电子迁移率非常高，持续光电导量也很大，这表明超导对半导体的穿透长度很长并且可以变化很大。我们测量了这些器件在光照下的超导特性。在超导薄膜间隙宽度在0.2-0.3μm以下的器件中，电流-电压曲线在4.2K时出现滞后现象，这是约瑟夫森结的典型特征。此外，临界电流（电阻突然增加点）随着光照的增加而增加。根据这些结果，我们成功地通过照明改变了介观器件的超导特性。使用本次资助购买的交流电阻桥，我们还测量了量子霍尔体系中二维电子系统（GaAs/AlGaAs异质结构）中电容的磁场依赖性。已经发现，霍尔平台处的电容底值不是由栅极面积决定，而是由栅极的边缘长度决定。这些结果无法用磁电容的传统解释来解释，磁电容的电容与二维电子气的态密度直接相关。我们建议建立一个模型，底部值由边缘状态的面积确定。根据该模型，估计了边缘态的宽度并与最近的理论进行了比较。