Effects of Different Plasma Energy Treatments on n-Type Al_0.4Ga_0.6N Material

Electronic properties, surface chemistry and surface morphology of plasma-treated n-Al_0.4Ga_0.6N material are studied by electrical contact measurements, atomic force microscopy and x-ray photoemission spectroscopy. Although excessive etching can cause the surface roughness to significantly increase, the nitrogen vacancies V_N produced by the excessive etching can be compensated for by the negative effects of the rougher surface. Thus, V_N produced by excessive etching plays a key role in Ohmic contact of high-Al content AlGaN and it can reduce Ohmic contact resistance. The effect of rapid thermal annealing on the performance of n-Al_0.4Ga_0.6N can significantly reduce the etching damage caused by excessive etching.