Influence of GaN capping on performance of InAlN/AlN/GaN MOS-HEMT with AI_2O_3 gate insulation grown by CVD

摘要

We investigate InAlN/AlN/GaN-based MOS-HEMTs with and without a 20 A-GaN capping below an Al_2O_3-insulator. An excellent reduction of the leakage current, up-to 6 orders of magnitude, is observed in MOS-HEMT structures compared 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 transconduc-tance value g_(m,max) for the GaN-capped-MOS-HEMT is aboutrn10% higher than that lor the conventional Schottky-based-HEMT, while in the ease of uncapped devices g_(m,max) is about the same for both Scholtky 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-based-HEMT. Performance improvement of MOS structure can be explained by a mobility-dependent carrier depiction effect.