Influence of Ni Schottky contact thickness on two-dimensional electron-gas sheet carrier concentration of strained Al0.3Ga0.7N/GaN heterostructures

Abstract

Ni/Au Schottky contacts with thicknesses of either 50 Å/50 Å or 600 Å/2000 Å were deposited on strained Al0.3Ga0.7N/GaN heterostructures. Using the measured C-V curves and I-V characteristics at room temperature, the calculated density of the two-dimensional electron-gas (2DEG) of the 600 Å/2000 Å thick Ni/Au Schottky contact is about 9.13 × 1012 cm−2 and that of the 50 Å/50 Å. thick Ni/Au Schottky contact is only about 4.77 × 1012 cm−2. The saturated current increases from 60.88 to 86.34 mA at a bias of 20 V as the thickness of the Ni/Au Schottky contact increases from 50 Å/50 Å to 600 Å/2000 Å. By self-consistently solving Schrodinger's and Poisson's equations, the polarization charge sheet density of the two samples was calculated, and the calculated results show that the polarization in the AlGaN barrier layer for the thick Ni/Au Schottky contact is stronger than the thin one. Thus, we attribute the results to the increased biaxial tensile stress in the Al0.3 Ga0.7N barrier layer induced by the 600 Å/2000 Å thick Ni/Au Schottky contact.