Electro-thermo-mechanical transient modeling of stress development in AlGaN/GaN high electron mobility transistors (HEMTs)

In this paper, we present a coupled small-scale electro-thermal model for characterizing AlGaN/GaN HEMTs under direct current (DC) and alternating current (AC) power conditions for various duty cycles. The calculated electrostatic potential and internal heat generation data are then used in a large-scale mechanics model to determine the development of stress due to the inverse piezoelectric and thermal expansion effects. The electrical characteristics of the modeled device were compared to experimental measurements for validation as well as existing simulation data from literature. The results show that the operating conditions (bias applied and AC duty cycle) strongly impact the temperature within the device and the stress fluctuations during cyclic pulsing conditions. The peak stress from the inverse piezoelectric effect develops rapidly with applied bias and slowly relaxes as the joule heating increases the device temperature during the on state of the pulse leading to cyclic stresses in operation of AlGaN/GaN HEMTs.