Roles of hydrogen dilution on the microstructural and optoelectronic properties of B-doped nanocrystalline Si:H thin films

Abstract

We report on the roles of hydrogen dilution on the microstructural and optoelectronic properties of boron-doped nanocrystalline silicon thin films grown by plasma-enhanced chemical vapor deposition on glass substrates, through x-ray diffraction, scanning electron microscope, Raman scattering, optical transmission, temperature-dependent dark conductivity, and elastic recoil detection analysis (ERDA) measurements. The grain size, crystallinity, absorption coefficient, refractive index, and conductivity are found to decrease basically with increasing hydrogen dilution ratio ΔH. The Tauc’s optical band gap is found to increase with ΔH due to the quantum size effect. By the aid of hydrogen ion bombardment effect [J. Appl. Phys. 93, 1262 (2003)] as well as the hydrogen-induced annealing effect, the clear increase of hydrogen content with ΔH and the different hydrogen distribution from ERDA help us to elucidate the correlation of hydrogen dilution with the crystallinity and grain size. The argument has been further supported by a simple absorption model and the yielded refractive index and absorption coefficient.

Gas doping ratio effects on p-type hydrogenated nanocrystalline silicon thin films grown by hot-wire chemical vapor deposition

“…Furthermore, for the PECVD samples the boron doping efficiency, which is the ratio of the carrier concentration to the boron concentration in the solid phase, is also very low (10-20%) [12]. Therefore, the highest conductivity hitherto reported for p-type nc-Si:H prepared by PECVD is only around 10 S/cm [12,13], whereas for HWCVD p-type nc-Si:H a conductivity value as high as 100 S/cm has been reported [14,15], which is ten times higher than the PECVD samples. Therefore, HWCVD is becoming a promising method to achieve highly conductive p-type nc-Si:H films.…”

Grown Low‐Temperature Microcrystalline Silicon Thin Film by VHF PECVD for Thin Films Solar Cell

“…It was shown that the grain size increased from 11.4 to 45.6 nm with decreasing the silane concentration from 13 to 4%. It is reported that hydrogen is supposed to enhance the surface diffusion of adsorbed precursors, preferentially etch off the disordered phase, and assist Si-Si bonding reconstruction within a subsurface layer [11,12]. As expected, H 2 dilution is a very sensitive method to realize crystallization of the amorphous Si thin films.…”

Relationship of microstructure properties to oxygen impurities in nanocrystalline silicon photovoltaic materials

“…The nanocrystalline silicon growth resulted from a complex synergy between surface and bulk reactions of impinging SiH x radicals, atomic hydrogen, and ion species. 30,31 As we can see from Table I,…”