有偏和无偏照明对无掺杂剂GaAs/AlGaAs 2DEG的影响
Effects of biased and unbiased illuminations on dopant-free GaAs/AlGaAs 2DEGs
摘要：
照明是在低温下进行的无掺杂剂的二维电子气体（2DEG）的不同深度，在无偏置（栅极接地）和偏置（栅极在正或负电压）的条件下。位于距离表面超过70 nm的2DEG中的无偏照明导致在给定电子密度下的迁移率的增益，主要由背景杂质的减少驱动。在更接近表面的2DEG中，无偏照明导致迁移率损失，由表面电荷密度的增加驱动。用正施加的栅极电压执行的偏置照射导致迁移率增益，而用负施加的电压执行的偏置照射导致迁移率损失。迁移率增益（损失）的幅度随着2DEG深度而减弱，并且可能由表面电荷密度的减少（增加）驱动。值得注意的是，这种迁移率增益/损失是完全可逆的，通过执行另一个偏置照明与适当的栅极电压，提供了n型和p型欧姆接触。实验结果与玻尔兹曼输运理论建模，并讨论了可能的机制。
英文摘要：
Illumination is performed at low temperature on dopant-free two-dimensional electron gases (2DEGs) of varying depths, under unbiased (gates grounded) and biased (gates at a positive or negative voltage) conditions. Unbiased illuminations in 2DEGs located more than 70 nm away from the surface result in a gain in mobility at a given electron density, primarily driven by the reduction of background impurities. In 2DEGs closer to the surface, unbiased illuminations result in a mobility loss, driven by an increase in surface charge density. Biased illuminations performed with positive applied gate voltages result in a mobility gain, whereas those performed with negative applied voltages result in a mobility loss. The magnitude of the mobility gain (loss) weakens with 2DEG depth, and is likely driven by a reduction (increase) in surface charge density. Remarkably, this mobility gain/loss is fully reversible by performing another biased illumination with the appropriate gate voltage, provided both n-type and p-type ohmic contacts are present. Experimental results are modeled with Boltzmann transport theory, and possible mechanisms are discussed.
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