Effects of buffer acceptors on breakdown voltages of AlGaN/GaN HEMTs with a high-k passivation layer

We analyze AlGaN/GaN HEMTs with a buffer layer where a deep acceptor above the midgap is considered, and studied how the off-state breakdown voltage is influenced by introducing a high-k passivation layer. As a result, it is shown that the breakdown voltage improves as in a case with a deep donor whose energy level is set equal to the acceptor's energy level, and in this case the breakdown voltage becomes a little higher in the region where the relative permittivity of the passivation layer is high. It is also shown that when the deep-acceptor's energy level is deeper, the breakdown voltage becomes higher in the highk region because the buffer leakage current becomes smaller.