Effect of trapped charge in AlGaN/GaN and AlGaN/InGaN/GaN heterostructure by temperature dependent threshold voltage analysis

The effect of trap energy states in AlGaN/InGaN/GaN heterostructure is investigated by temperature dependent threshold voltage measurement from 298 K to 373 K. It is found that the threshold voltage of AlGaN/InGaN/GaN structure decreases from - 6.52 V to - 6.90 V with temperature increase from 298 K to 348 K. But for the temperature higher than 348 K, the threshold voltage starts to increase and reaches to - 6.75 V at 373 K. However, the threshold voltage for AlGaN/GaN structure decreases consistently from −5.32 V to −6.4 V for entire range of temperature. The decrease of threshold voltage is attributed to the surface donor trap charges for both the heterostructures. Furthermore, the acceptor trap charges might have contributed for temperature above 348 K, and hence the increase of threshold voltage is observed in AlGaN/InGaN/GaN heterostructure. Higher crystal defects, resulted from lower growth temperature, might be responsible for the formation of these acceptor trap levels in InGaN layer.