Effect of deposition technique of SiNx passivation layer on the electrical DC and RF properties of AlGaN/GaN HEMTs

Abstract

In this paper, we present the results of a comparative analysis of two alternative SiNx passivation techniques of AlGaN/GaN high electron mobility transistor (HEMT) manufactured using identical epitaxial structure and fabrication processes. AlGaN/GaN HEMT has demonstrated excellent device characteristics, making them excellent candidates for high power, high frequency, and low noise applications. However, the full potential of GaN HEMTs in large signal operation at high frequency is limited by trapping effects and leakage currents at the interface between the epitaxial structure and passivation layer. A SiNx passivation layer has commonly been used to prevent electron trapping at the surface by providing extra positive charges to neutralize trapped negative electrons on the surface. This comparative study investigates the effects of a 75 nm SiNx passivation layer fabricated using both plasma-enhanced chemical vapor deposition (PECVD) and inductively coupled plasma chemical vapor deposition (ICPCVD) techniques on the DC and RF performance of the transistor.