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

The Mg acceptor activation mechanism and hole transport characteristics in AlGaN alloy with Mg doping concentration(～ 10;cm;) grown by metal–organic chemical vapor deposition（MOCVD） are systematically studied through optical and electrical properties. Emission lines of shallow oxygen donors and（V;complex）;as well as V;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 Mgdoped Al;Ga;N（x = 0.23, 0.35） are 172 meV and 242 meV, and the hole concentrations at room temperature are 1.2×10;cm;and 3.3× 10;cm;, 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.