Analysis of Si3N4 passivation effect by self-consistent electro-thermal-mechanical simulation in AlGaN/GaN heterostructure HEMTs

The effect of surface passivation on AlGaN/GaN higher electron mobility transistors (HEMT) has been investigated with electro-thermal-mechanical coupling. Electrical, mechanical and thermal properties of AlGaN/GaN HEMTs before and after passivation are analyzed. The drain current increases after passivation because surface passivation reduces the surface state density. Also, planar stress and elastic energy were decreased, as compare the devices with passivation and without passivation conditions. Also, the effect of different lattice heating (uniform heating, no lattice heating) has been studied in this experiment. This shows that the elastic energy in device with uniform heating is lower than that without lattice heating. In this investigation we found that uniform heating will provide elastic energy lower than critical value and with the use of Si3N4 the temperature distribution is very uniform which in turn reduces the stress in AlGaN/GaN HEMTs.