Suppression Of Gate Leakage Current In I-Algan/Gan Hetero-Structures By Insertion Of Anodic Al2o3 Layer And Influence Of Thermal Annealing On Channel Electrons

We have investigated electrical properties of Ni/anodoc-Al2O3/i-AlGaN/GaN gate structures formed by insertion of a thin anodic Al2O3 layer, and the influence of surface preparation or thermal stressing of bare i-AlGaN/GaN heterostructures on channel electrons. The gate structure effectively suppressed the reverse leakage current down to 10(-6)-10(-7)A/cm(2) range depending on the wafer, after optimum annealing in N-2. Measured C-V curves indicated a small density of states at anodic-Al2O3/AlGaN interface. Hall effect measurements revealed that 2DEG density of bare i-AlGaN/GaN samples is considerably affected by the surface preparation condition, and that a high temperature thermal stressing in O-2 ambient rather degrades the electron mobility of 2DEG, suggesting enhanced incorporation of oxygen in AlGaN layer. (c) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.