Low-Pressure Chemical Vapor Deposition SiN Process Study and Its Impact on Interface Characteristics of AlGaN/GaN MISHEMTs.

This study employed low-pressure chemical vapor deposition (LPCVD) SiN as both the gate dielectric layer and surface passivation layer, systematically investigating the effects of different growth conditions on the dielectric layer quality, two-dimensional electron gas (2DEG) characteristics, interface trap density, and devices' performance, thereby optimizing the growth parameters of LPCVD SiN. The experiment investigated the effects of growth parameters such as the growth temperature, chamber pressure, and gas flow ratio on the growth rate of SiN during the process of growing SiN using the LPCVD technique. Further studies were performed to analyze the impact of SiN introduction on the 2DEG performance. The results indicated that both Si-rich and N-rich SiN compositions could enhance the 2DEG density improvement induced by SiN passivation. The impact of the gas flow ratio on the interface trap density is studied. Through the quantitative characterization of the interface trap density using the pulse-mode I-V method and frequency-dependent capacitance-voltage (C-V) measurement, the results show that the interface trap density decreases with an increased Si-to-N ratio.