Doping properties of boron-doped microcrystalline silicon from B2H6 and BF3:: material properties and solar cell performance

We have studied the doping properties of boron-doped hydrogenated microcrystalline silicon (muc-Si:H) deposited by glow-discharge plasmas of different SiH4/H-2/B2H6 and SiH4/H-2/BF3 gas mixtures. Regardless of dopant source gas, the solid-phase doping efficiency (hole/boron concentration ratio) increases monotonically as the boron concentration (C-B) increases in the film, and it approaches unity at C-B > 10(20) atoms/cm(3), generating sufficient hole concentrations for solar cells. This doping behavior suggests that the impurity activation in muc-Si:H is independent of defect-compensation process in contrast to that in hydrogenated amorphous silicon. Although material properties reveal no dependence on the type of dopant source gas, muc-Si:H p-i-n solar cells with players doped from BF3 provide higher conversion efficiencies than those from B2H6 at a lower C-B range of <3 x 10(19) atoms/cm(3). Possible effects of the p-layer thickness on the doping properties are discussed. (C) 2004 Elsevier B.V. All rights reserved.