Trapped charge effects in AlGaN/GaN metal-oxide-semiconductor structures with Al2O3and ZrO2gate insulator

Trapped charge effects in AlGaN/GaN metal-oxide-semiconductor (MOS) structures with Al 2 O 3 and ZrO 2 gate insulator were analyzed by capacitance–voltage ( C – V ) measurement. The influence of the voltage sweep range on the threshold voltage and capacitance hysteresis is presented first. The trapping effects are investigated by C – V measurement at varied voltage sweep rates ranged between 100 and 0.01 V s −1 . The threshold voltage V th and the hysteresis width Δ V hyst depended significantly on the sweep rate ( V th shift and Δ V hyst change up to ∼1.3 V). The Al 2 O 3 - and ZrO 2 -based MOS structures exhibited opposite V th and Δ V hyst changes with the sweep rate. This points to different types of trapped charge in the structures investigated. The trapping effects that we observe resulted both from the capture/emission of electrons at the insulator/AlGaN interface and from the negative or positive fixed charge in the Al 2 O 3 or ZrO 2 insulators, respectively, at their different densities. This shows that C – V analysis with different voltage sweep rate might be a useful tool for an evaluation of trapped charge in MOS structures.