Self-consistent electro-thermal simulation of AlGaN/GaN HEMTs for reliability prediction

During the last few years, AlGaN/GaN high electron mobility transistors (HEMTs) have been intensively studied for high-frequency high-power applications. In spite of this great interest, device reliability is still an important challenge for the wide deployment of AlGaN/GaN HEMT technology. To fully understand reliability in these devices, it is necessary to consider the electrical, mechanical and thermal properties of the operating AlGaN/GaN transistors. Since AlGaN and GaN are both piezoelectric materials, the coupling between electric field and mechanical characteristics gives rise to changes in the stress/strain field and thus electronic properties of HEMTs [1]. Most published work has focused on the role of the inverse piezoelectric effect induced by the electric field [2], however, lattice heating also changes the mechanical properties of HEMTs and its effect on device reliability is also important. In this paper, we have developed the first fully-coupled electro-thermo-mechanical simulation of AlGaN/GaN HEMTs to study the reliability of these devices as a function of bias voltage and operating temperature. In addition, we have compared the numerical results of our simulations with high resolution thermo-reflectance measurements [3], obtaining excellent agreement.