The band alignment at an Al2O3/SrTiO3 heterointerface forming a two-dimensional electron gas (2DEG) was investigated using scanning photocurrent microscopy (SPCM) in an electrolyte-gated environment. We used a focused UV laser source for above-the-bandgap illumination on the SrTiO3 layer, creating electron-hole pairs that contributed to the photocurrent through migration towards the metal electrodes. The polarity of the SPCM signals of a bare SrTiO3 device shows typical p-type behavior at zero gate bias, in which the photogenerated electrons are collected by the electrodes. In contrast, the SPCM polarity of 2DEG device indicates that the hole carriers were collected by the metal electrodes. Careful transport measurements revealed that the gate-dependent conductance of the 2DEG devices exhibits n-type switching behavior. More importantly, the SPCM signals in 2DEG devices demonstrated very unique gate-responses that cannot be found in conventional semiconducting devices, based on which we were able to perform detailed investigation into the electronic band alignment of the 2DEG devices and obtain the valence band offset at the heterointerface.

译文

:使用扫描光电流显微镜(SPCM)在电解质门控环境中研究了形成二维电子气(2DEG)的Al2O3 / SrTiO3异质界面处的能带排列。我们使用聚焦的UV激光源在SrTiO3层上进行带隙以上照明,从而创建电子-空穴对,这些电子-空穴对通过向金属电极的迁移而有助于光电流。裸露的SrTiO3器件的SPCM信号的极性在零栅极偏置下显示出典型的p型行为,其中光生电子被电极收集。相反,2DEG器件的SPCM极性表明空穴载流子被金属电极收集。仔细的传输测量表明,2DEG器件的依赖于栅极的电导表现出n型开关行为。更重要的是,2DEG器件中的SPCM信号表现出非常独特的门响应,这是常规半导体器件中找不到的,基于此,我们能够对2DEG器件的电子能带对准进行详细研究,并获得价带偏移。异类接口。

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