Strain effects in SiN-passivated GaN-based HEMT devices

The use of a passivating layer can reduce or even eliminate surface effects responsible for limiting both the RF current and breakdown voltage of AlGaN/GaN HEMTs. To study the effect of passivation on electrical characteristics of GaN-based devices, we have developed a macroscopic model of strain in SiN/AlGaN/GaN heterostructure, considering the system as a free-standing one. Basing on the strain results, we have calculated the strain map for a SiN-passivated structure and the electron sheet charge density in the channel. Results have been compared with experimental measurements and with an alternative passivation model.