Optical properties and local bonding configurations of hydrogenated amorphous silicon nitride thin films

Abstract

We report on the optical properties and local bonding configurations of both as-deposited and postannealed hydrogenated amorphous silicon nitride ͑a-SiN x :H͒ thin films grown on crystalline Si substrates with x approximately 1.2± 0.1. Ultraviolet optical reflection and infrared ͑IR͒ absorption measurements were applied to characterize the films. A method simply based on optical reflection spectra is proposed for accurate determination of the optical band gap, band tail, wavelength-dependent refractive index and extinction coefficient, as well as the film thickness, suggesting that the Tauc-Lorentz ͓G. E. Jellison, Jr. and F. A. Modine, Appl. Phys. Lett. 69, 371 ͑1996͒; 69, 2137 ͑1996͔͒ model with the inclusion of Urbach tail is the optimal one to describe the optical response of a-SiN x : H films. The yielded optical parameters can be related well to the film microstructure as revealed by the IR absorption analysis. These results have implications for future deposition controlling and device applications.

A comparison of structures and properties of SiNx and SiOx films prepared by PECVD

“…In Fig. 4a, the absorption bands are assigned as: H-Si-N 3 symmetric stretching mode at 951 cm − 1 , Si 3 N 4 symmetric stretching mode at 871 cm − 1 , H 2 -Si-N 2 symmetric stretching mode at 820 cm − 1 , Si 3 -Si-N symmetric stretching mode at 794 cm − 1 , and H 2 -Si-N 2 asymmetric stretching mode at 740 cm − 1 [10]. Other IR peaks, such as 610 cm − 1 and 1106 cm − 1 , were originated from the Si substrate and native oxide, respectively.…”

Modified Tauc–Lorentz dispersion model leading to a more accurate representation of absorption features below the bandgap

“…In some cases, this approach demonstrated an improved description of the optical dielectric response for the materials such as, for example, high-κ dielectric films [40,62,63], hydrogenated amorphous silicon nitride (a-SiN x :H) films [64] and titanium dioxide (TiO 2 ) thin films [65,66]. However, the absorption below the band gap often does not correspond to the Urbach tail and the simple combination of Eq.…”

Thermal stability of amorphous silicon/silicon nitride stacks for passivating crystalline silicon solar cells

“…The density of the PECVDdeposited silicon nitride increases with increasing deposition temperature. 12 In this work we deposit the SiN x capping layer at higher temperatures ͑300 and 400°C͒ than the passivating a-Si: H film to improve the thermal stability of the surface passivation significantly over the status demonstrated so far.…”