The coexistence of two-dimensional electron and hole gases in GaN-based heterostructures

The formation of two-dimensional carrier gases in gated GaN/AlGaN/GaN heterostructures is investigated theoretically. It is shown that under certain conditions a two-dimensional hole gas at the upper GaN/AlGaN interface can be formed in addition to the two-dimensional electron gas at the lower AlGaN/GaN interface. For the calculations, a Schrdinger-Poisson solver and a simple analytical model developed in the present work are used. Conditions for the formation of a two-dimensional hole gas are elaborated. It is shown that once a two-dimensional hole gas is created, it shields the coexisting two-dimensional electron gas which will result in a diminishing effect of the gate voltage on the two-dimensional electron gas.