AlGaN/GaN MOSHFETs with HfO_2 gate oxide: A simulation study

摘要

Two-dimensional device simulations of a HfO_2/AlGaN/GaN metal-oxide-semiconductor-heterostructure FET (MOSHFET) have been carried out based on the drift-diffusion model focusing on the effects of HfO_2/ AlGaN interface properties. In the case of MOSHFETs with no trap at the HfO_2/AlGaN interface, the trans-conductance was found to decrease at large V_(cs) due to channel formation at the HfO_2/AlGaN interface, resulting in a plateau structure of g_m. When the interface states were incorporated at the HfO_2/AlGaN interface, g_m decreased due to electron capture by the trap at a smaller gate voltage than the onset of g_m decrease for the case with no trap at the HfO_2/AlGaN interface. This is because the trap level reached E_F earlier than the channel formation at the HfO_2/AlGaN interface. This resulted in a peak structure of the g_m when the interface states were deep, which is consistent with experimental results. It was pointed out that if the trap concentration was less than 4×10~(11) cm~(-2), the threshold voltage shift was less than 0.3 V and the g_m decrease was less than 10%.