Growth of Wide-Bandgap Nanocrystalline Silicon Carbide Films by HWCVD: Influence of Filament Temperature on Structural and Optoelectronic Properties

Silicon carbide (SiC) thin films have been deposited using a hot-wire chemical vapor deposition technique on quartz substrates with a mixture of silane, methane, and hydrogen gases as precursors at a reasonably high deposition rate of approximately 15 nm/min to 50 nm/min. The influence of the filament temperature (T (F)) on the structural, optical, and electrical properties of the SiC film has been investigated using x-ray diffraction, Raman scattering, Fourier-transform infrared spectroscopy, x-ray photoelectron spectroscopy, ultraviolet-visible-near infrared transmission spectroscopy, and dark conductivity (sigma (d)) studies. Films deposited at low T (F) (1800A degrees C to 1900A degrees C) are amorphous in nature with high density of Si-Si bonds, whereas high-T (F) (a parts per thousand yen2000A degrees C) films are nanocrystalline embedded in an amorphous SiC matrix with higher concentration of Si-C bonds and negligible concentration of Si-Si bonds. The bandgap (E (g)) varies from 2.5 eV to 3.1 eV and sigma (d) (50A degrees C) from similar to 10(-9) Omega(-1) cm(-1) to 10(-1) Omega(-1) cm(-1) as T (F) is increased from 1900A degrees C to 2200A degrees C. This increase in E (g) and sigma (d) is due to microstructural changes and unintentional oxygen doping of the films.