Fast and slow traps in Al2O3/(GaN)/AlGaN/GaN heterostructures studied by conductance technique

Influence of interface traps at Al2O3/(GaN)/AlGaN interface at low and high frequency on equivalent parallel conductance of Al2O3/(GaN)/AlGaN/GaN heterostructure capacitor was studied. By the conductance measurements two types of traps were identified in the measured structure. The traps differ in time constants by more than one order in magnitude. Fast traps with low time constants have narrow energy distribution and are probably located in the semiconductor energy gap close to the insulator semiconductor interface. Slow traps have wider distribution and are assumed to be directly at the insulator semiconductor interface. The presence of the fast traps which are able to respond to external ac signal is given into connection with the recently published increase of the structure capacitance in the plateau region with decreasing frequency.