Current-voltage characteristics of GaN and AlGaN p-i-n diodes

The current-voltage characteristics of GaN and Al0.08Ga0.92N p-i-n diodes were investigated. The experimental p-i-n structures were grown by MOCVD on 6H-SiC with Si and Mg as dopants. The i region was formed by simultaneously doping with donor and acceptor impurities during growth. Analysis of the current-voltage characteristics showed that current flow in the p-i-n diodes is due to either drift of thermally excited holes or electron-hole recombination in the i region via impurity centers—just as predicted by the Ashley-Milnes theory. These impurity centers are attributed to Mg acceptor levels.