AlGaN/GaN HEMT Degradation: An Electro-Thermo-Mechanical Simulation

We present fully self-consistent simulation results based on an electro-thermo-mechanical model of a typical AlGaN/GaN HEMT structure. The mechanical stress state is analyzed under different dc operating conditions in view of possible dislocation formation and movement by comparing simulated elastic energy densities and resolved shear stresses with theoretically predicted values. In particular, we find nonzero resolved shear stress on all wurtzite slip systems, with relevant values especially at high dc power. This could allow formation and movement of dislocations, leading to device degradation.