Analysis of high-k passivation-layer effects on buffer-related breakdown and current collapse in AlGaN/GaN HEMTs

We analyze breakdown characteristics and current collapse in AlGaN/GaN HEMTs, with the passivation layer's relative permittivity er as a parameter. It is shown that the off-state breakdown voltage is considerably enhanced by introducing a high-k passivation layer because the electric field at the drain edge of the gate is weakened and the buffer leakage current is reduced. The breakdown voltage in the high-epsilon(r) region increases when the gate voltage is changed from -8 to -10V, because the buffer leakage current is reduced. It is also shown that drain lag and current collapse in AlGaN/GaN HEMTs could be reduced by introducing a high-k thick passivation layer, because the electric field at the drain edge of the gate is reduced, leading to less electron injection into the buffer layer and weaker buffer trapping effects. (C) 2015 The Japan Society of Applied Physics