Identification of Microscopic Hole-Trapping Mechanisms in Nitride Semiconductors

Hole trapping has been observed in nitride heterostructure devices, where the Fermi level is in the vicinity of the valence-band maximum. Using hybrid density functional calculations, we examine microscopic mechanisms for hole trapping in GaN and AlN. In a defect-free material, hole trapping does not spontaneously occur, but trapping can occur in the vicinity of impurities, such as C—a common unintentional impurity in nitrides. Using Schrödinger–Poisson simulations, we assess the effects of C-derived hole traps on N-face high-electron mobility transistors, which we find to be more detrimental than the previously proposed interface traps.