Enhanced field-assisted passivation and optical properties improvement of PECVD deposited SiNx:H thin film

Abstract

This article investigates field-assisted passivation in hydrogenated silicon nitride (SiNx:H) with reduced absorption loss by utilizing two different purities of saline (SiH4) gas and their deposition conditions using plasma-enhanced chemical vapor deposition (PECVD). The impact of varying NH3:SiH4 flow rate using SiH4 (gas 2) is better and more reliable than SiH4 (gas 1) in terms of the refractive index (R.I), deposition conditions and lifetime. A gas ratio (GR) of 1.3 results in an optimal R.I of 2.06, thickness of 73.62 nm, and a deposition rate of 0.98 nm/s, achieving the highest optical transmittance of 93.33 % at 300 °C, with an improved lifetime of 473.45 μs calculated for SiH4 gas 2 as compared to gas 1. The bandgap of GR 1.3 is calculated as 3.28 eV using Tauc plot since this condition is best for single-layer antireflection coating (SLAR). Capaciatance-Voltage (CV) measurements were carried out for different flow rates of gas 2 at 10 kHz and 1 MHz to carry out defect interface density (Dit). However, the Dit effect varies with flow rates as 2.35 × 1012 to 3.925 × 1013 cm2/eV. Fixed charge density (Qf) varies as we go up to nitrogen-rich content and reaches up to 6.6 × 1012 (cm−2). These results indicate the importance of precise control over gas conditions to optimize SiNx:H films for advanced photovoltaics applications. © 2025 Elsevier B.V.