Defects and Defect Reactions in Semiconductor Nitrides

We report a comprehensive investigation of native point defects and impurities in GaN, MN, and AlGaN alloys, with the goal of understanding doping limitations in nitride semiconductors.Unintentional incorporation of impurities (mainly oxygen) explains the tendency of nitride semiconductors to exhibit n-type conductivity.Silicon is the n-type dopant of choice; it remains shallow in AlGaN up to high Al content, while oxygen undergoes a DX transition.Experimental evidence for DX centers will be discussed.In p-type material, Mg doping is hindered by an increase in ionization energy with increasing Al content in AlGaN, and by nitrogen vacancies acting as compensating centers.Complex formation between magnesium and oxygen and between magnesium and nitrogen vacancies will be discussed.