R. Tsurumaki, N. Noda, K. Horio
Shibaura Institute of Technology, Japan
pp. 121 - 125
Keywords: GaN HEMT, field plate, current collapse, buffer layer, deep acceptor, two-dimensional analysis
In AlGaN/GaN HEMTs, slow current transients are often observed even if the gate voltage VG or the drain voltage VD is changed abruptly. This is called gate lag or drain lag, and is problematic for circuit applications. The slow transients mean that dc I-V curves and RF I-V curves become quite different, resulting in lower RF power available than that expected from dc operation. This is called current collapse. These are serious problems, and many experimental works are reported, but relatively small number of theoretical works are made. In previous theoretical works, the buffer is treated as undoped, and a deep donor and a deep acceptor are considered in it. Recently, a Fe-doped buffer layer is often adopted, and Fe acts as a deep acceptor. Therefore, in this work, we have made simulations of field-plate AlGaN/GaN HEMTs with a buffer layer including only deep acceptors, and found that the buffer-related lags and current collapse are quite similar between the two cases.