Investigation of Mg doping in high-Al content p -type Alx Ga1-x N (0.3<x<0.5)

A study of Mg doping of Alx Ga1-x N up to x~50% using microstructural and electrical probes is reported. The viability of effective p -type doping is defined by a minimum concentration of Mg required to offset the background impurities and, more importantly, a maximum limit above which inversion domains and structural defects start to nucleate, accompanied by a rapid degradation of electrical transport. Resistivity of 10 Ω cm and free hole concentrations above 1017 cm-3 are achieved for Alx Ga1-x N up to x~50% within an optimum window of Mg incorporation.