Abstract:

Ni/Au Schottky contacts with thicknesses of either 50 Å/50 Å or 600 Å/2000 Å were deposited on strained Al_0.3Ga_0.7N/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 Al_0.3Ga_0.7N barrier layer induced by the 600 Å/2000 Å thick Ni/Au Schottky contact.

Key words: AlGaN/GaN heterostructure, Schottky contact thicknesses, two dimensional electron gas, tensile stress