Temperature dependent lateral and vertical conduction mechanisms in AlGaN/GaN HEMT on thinned silicon substrate

Abstract

This paper presents the influence of Si substrate thinning by grinding and dicing on the mechanical and electrical properties of AlGaN/GaN HEMT grown on 6-inch Si substrate. By experimentally removing 96% of the Si substrate, an increase in the lateral breakdown voltage by 13% is achieved for a wide temperature range. A decreasing vertical breakdown voltage with substrate thinning shows the necessity of substrate replacement to maintain the vertical isolation. Poole-Frenkel and space charge limited conduction mechanisms are identified for the vertical leakage in forward and reverse bias down to thicknesses of 200 μm, respectively. The increase in chip bow and the resulting increase in tensile strain in the epitaxial layers resulting from the substrate removal are correlated to a 40% decrease in 2DEG charge carrier concentration along with a 27% increase in threshold voltage. These findings are explained by strain-induced gate barrier and polarization charge variations.