Self-assembled nc-Si-QD/a-SiC thin films from planar ICP-CVD plasma without H2-dilution: a combination of wide optical gap, high conductivity and preferred 〈220〉 crystallographic orientation, uniquely appropriate for nc-Si solar cells

Abstract

Spontaneous miniaturization of self-assembled nc-Si-QDs with preferred 〈220〉 crystallographic orientation and a rapid synthesis of superior quality nc-Si-QD/a-SiC thin films with enhanced crystallinity, maintaining a combination of wide optical gap and simultaneous high electrical conductivity, has been attained from (SiH₄ + CH₄)-plasma, without any additional H₂-dilution in inductively coupled plasma CVD. The optical gap widens due to the Si–C bonds in the amorphous network and the increased quantum confinement effect on the miniaturized Si-QDs. CH₄ acts as the dual source of both C and atomic-H. High density of atomic-H available in the planar ICP promotes simultaneously the Si crystallization and its growth along the thermodynamically favored 〈220〉 crystallographic orientation, thereby contributing easier electrical transport, particularly at devices in superstrate configuration. After imminent doping, these could be efficiently utilized as window layers in third generation all-silicon solar cells.