Simulation of Widegap Semiconductor Devices

虽然在AlGaN/GaN hemt中有许多关于电流崩溃和慢电流瞬态（栅极滞后和漏极滞后）的实验结果，但很少有理论研究。因此，我们对缓冲层中考虑深层供体和深层受体的AlGaN/GaN hemt进行了二维分析，发现可以再现滞后现象和电流崩溃现象。特别地，研究表明栅极滞后与AlGaN/GaN hemt相对较高的源端接入电阻相关，而漏极滞后可能是电流崩溃的主要原因。当深受体密度较高和失态漏极电压较高时，电流崩溃更为明显。结果表明，为了使AlGaN/GaN hemt中的电流崩溃最小化，缓冲层中的受体密度应该降低，尽管当栅极长度较短时电流截止行为可能会降低。

Although many experimental results are reported on current collapse and slow current transients (gate lag and drain lag) in AlGaN/GaN HEMTs, few theoretical works are performed. Therefore, we have made two-dimensional analysis of AlGaN/GaN HEMTs in which a deep donor and a deep acceptor are considered in the buffer layer, and found that lag phenomena and current collapse could be reproduced. Particularly, it is shown that gate lag is correlated with relatively high source access resistance of AlGaN/GaN HEMTs, and that drain lag could be a major cause of current collapse. It is also shown that current collapse is more pronounced when the deep-acceptor density is higher and when an off-state drain voltage is higher. It is concluded that to minimize current collapse in AlGaN/GaN HEMTs, an acceptor density in the buffer layer should be made low, although current cutoff behavior may be degraded when the gate length is short.