Thermal stability of W, WSi<i>x</i>, and Ti/Al ohmic contacts to InGaN, InN, and InAlN

Abstract

W, WSi0.44, and Ti/Al contact properties were examined on n+In0.65Ga0.35N, InN, and In0.75Al0.25N. W was found to produce low specific contact resistance (dc∼10−7 Ω cm2) ohmic contacts to InGaN, with significant reaction between metal and semiconductor occurring at 900 °C mainly due to out diffusion of In and N. WSix showed an as-deposited dc of 4×10−7 Ω cm2 but this degraded significantly with subsequent annealing at ≥600 °C. Ti/Al contacts were stable to ∼600 °C (dc∼4×10−7 Ω cm2 at ≤600 °C). The surfaces of these contacts remained smooth to 800 °C for W and WSix and 650 °C for Ti/Al. InN contacted with W and Ti/Al produced ohmic contacts with dc∼10−7 Ω cm2 and for WSixdc∼10−6 Ω cm2. All remained smooth to ∼600 °C, but exhibited significant interdiffusion of In, N, W, and Ti, respectively, at higher temperatures. The contact resistances for all three metalization schemes were ≥10−4 Ω cm2 on InAlN, and degraded with subsequent annealing.