Trap characterization of in-situ metal-organic chemical vapor deposition grown AlN/AlGaN/GaN metal-insulator-semiconductor heterostructures by frequency dependent conductance technique

Frequency dependent conductance measurements were employed to study the trapping effects of in-situ metal-organic chemical vapor deposition grown AlN/AlGaN/GaN metal-insulator-semiconductor heterostructures (MISHs). Conventional fitting method could not be used to explain the experimental parallel conductance (G(p)/omega) results. Alternatively, experimental G(p)/omega values were resolved into two fitting curves for gate voltages (-1.2 to -1.8 V) near the threshold voltage (V-th) by a fitting model. In the low frequency region (<=<50 kHz), the G(p)/omega values can be fitted into a single curve. On the other hand, in the high frequency region, two fitting curves were necessary. The results using this model explicitly yielded two types of traps existing in the AlN/AlGaN/GaN MISHs, one due to the insulating AlN layer and the other caused by the AlGaN barrier layer. (C) 2011 American Institute of Physics. [doi :10.1063/1.3614556]