Mg acceptor activation mechanism and hole transport characteristics in highly Mg-doped AlGaN alloys*

Abstract

The Mg acceptor activation mechanism and hole transport characteristics in AlGaN alloy with Mg doping concentration (∼ 1020 cm−3) grown by metal–organic chemical vapor deposition (MOCVD) are systematically studied through optical and electrical properties. Emission lines of shallow oxygen donors and (VIII complex)1− as well as V N 3 + and neutral Mg acceptors are observed, which indicate that self-compensation is occurred in Mg-doped AlGaN at highly doping levels. The fitting of the temperature-dependent Hall effect data shows that the acceptor activation energy values in Mg-doped Al x Ga1 − x N (x = 0.23, 0.35) are 172 meV and 242 meV, and the hole concentrations at room temperature are 1.2 × 1018 cm−3 and 3.3 × 1017 cm−3, respectively. Therefore, it is believed that there exists the combined effect of the Coulomb potentials of the dopants and screening of the Coulomb potentials by a high hole concentration. Moreover, due to the high ionized acceptors’ concentration and compensation ratio, the impurity conduction becomes more prominent and the valence band mobility drops sharply at low temperature.