In situ SiN passivation of AlGaN/GaN HEMTs by molecular beam epitaxy

To improve the passivation process of AlGaN/GaN HEMTs, a unique passivation process has been developed in which an SiN passivation layer is deposited by MBE immediately following epitaxial growth of the HEMT structure. The effectiveness of this in situ passivation process is evaluated by comparing devices fabricated with this process to the conventional PECVD passivation process in which the SiN is deposited after gate metallisation. The improved material quality and the protection offered by the MBE-grown SiN may contribute to the significantly reduced dispersion and improved power performance measured for the wafer fabricated with the in situ passivation process.