Influence of GaN capping on performance of InAIN/AIN/GaN MOS-HEMT with Al_2o_3 gate insulation grown by CVD

摘要

We investigate InAIN/AIN/GaN-based MOS-HEMTs with and without a 20 A-GaN capping below an Al203-insulator. An excellent reduction of the leakage current, up-to 6 orders of magnitude, is observed in MOS-HEMT structures com-pared to Schottky-based-HEMTs, both with GaN capping. In the case of uncapped samples the reduction in the leakage current is 3 orders of magnitude. The maximal transconductance value g_(m,max) for the GaN-capped-MOS-I-IEMT is about 10% higher than that for the conventional Schottky-based-HEMT, while in the case of uncapped devices g_(m,max) is about the same for both Schottky and MOS-HEMT. Similarly the maximal-drain-current in the GaN capped MOS-HEMT is 950mA/mm, exhibiting an increase of 180mA/mm in comparison to the corresponding conventional Schottky-basedHEMT. Performance improvement of MOS structure can be explained by a mobility-dependent carrier depletion effect.