Piezoelectricity-induced schottky barrier height variations in AlGaN/GaN high electron mobility transistors

Drain current of AlGaN/GaN high electron mobility transistors (HEMTs) is measured to decrease/increase with in-plane tensile/compressive external strain. Such a trend is opposite to the conventional theory of direct piezoelectric effect on 2-D electron gas (2DEG). The reason is found to be the dependence of nickel gate barrier height on external strain, which strongly affects HEMTs' threshold voltage and 2DEG concentration. The Ni/AlGaN interface states are proposed to be responsible for strain-induced gate barrier variations, which are important for device performances and sensor applications.