Influence Of Pecvd Deposited Sinx Passivation Layer Thickness On In0.18al0.82n/Gan/Si Hemt

The influence of plasma enhanced chemical vapour deposited (PECVD) silicon nitride (SiNx) passivation film thickness on In0.18Al0.82N/GaN/Si heterostructures and HEMTs has been investigated. The formation of Si3N4 was confirmed by x-ray photoelectron spectroscopy (XPS) measurements. X-ray reflectivity (XRR) measurements reveal that both the density and roughness of the SiNx film increase with increasing film thickness. With an increase in SiNx film thickness, a significant increase in two-dimensional electron gas (2DEG) density, drain current, extrinsic transconductance and negative threshold voltage shift of the In0.18Al0.82/GaN/Si HEMTs are observed. An optimal thickness of SiNx is similar to 100 nm and it yields a substantial increase in 2DEG density (similar to 30%) with a minimum sheet resistance for In0.18Al0.82N/GaN/Si heterostructures. Furthermore, we correlate the observed SiNx film thickness-dependent electrical characteristics of In0.18Al0.82/GaN/Si HEMTs with the density of the SiNx film.