Influence of GaN capping on performance of InAlN/AlN/GaN MOS‐HEMT with Al2O3 gate insulation grown by CVD

Abstract

AbstractWe investigate InAlN/AlN/GaN‐based MOS‐HEMTs with and without a 20 Å‐GaN capping below an Al2O3‐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 transconductance value gm,max for the GaN‐capped‐MOS‐HEMT is about 10% higher than that for the conventional Schottky‐based‐HEMT, while in the case of uncapped devices gm,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‐based‐HEMT. Performance improvement of MOS structure can be explained by a mobility‐dependent carrier depletion effect. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)