A method to increase sheet electron density and mobility by vacuum annealing for Ti/Al deposited AlGaN/GaN heterostructures

摘要

Temperature dependence of sheet electron density (ns) and mobility (μ) for Ti/Al deposited AlGaN/GaN heterostructures annealed in vacuum has been investigated using Hall effect measurements. The vacuum annealing at 1020 K caused the increase in both ns and μ at room temperature, with the amount of one order of magnitude and 65%, respectively, as compared to without annealed sample. The amount of increase was much less for only Ti or Al deposited or totally thin Ti/Al deposited sample. The origin of the increase is attributed to tensile strain induced by vacuum annealing. The method is useful for reducing the ohmic contact resistivity and/or the access resistance between source and gate in AlGaN/GaN HEMTs.