Analysis of localized charge trapping behavior in AlGaN/GaN heterostructures

Long-time-constant charge trapping behavior in Al/sub x/Ga/sub 1-x/N/GaN heterostructure field effect transistor epitaxial layer structures is probed using scanning capacitance microscopy. Localized charged areas, induced by scanning with relatively high DC bias voltages applied between a proximal probe and sample, are imaged simultaneously with surrounding uncharged regions. Localized charge trapping is observed, and comparisons are made of trapping behavior for different samples based on growth technique, Al composition, and doping level. In samples grown by molecular beam epitaxy, localized structural features (Ga droplets) formed during growth induce significant increases in the amount of local charge trapping that occurs.