Surface passivation of crystalline silicon wafers by hydrogenated amorphous silicon probed by time resolved surface photovoltage and photoluminescence spectroscopy

Abstract

The passivation of crystalline silicon surfaces by ultrathin intrinsicand n-type a-Si:H films is studied by surface photovoltage (SPV)and photoluminescence (PL) measurements. Analyzing the influenceof a-Si:H film thickness, deposition temperature and hydrogen dilutionof the process gas, we come to the conclusion that the best interfacepassivation is reached at a substrate temperature of 200 - 230°C.The a-Si:H emitter thickness in the range 6 - 120 nm has no influenceon the a-Si:H/c-Si interface properties. Applying the field dependentSPV, the energetic density distribution of the interface states isdetermined. By passivating (100)-oriented float-zone silicon wafersby ultra-thin (6 nm) intrinsic a-Si:H films, a U-shaped distributionis obtained with a minimum of less than 2×1011eV-1cm-2 at mid-gapusing optimized deposition parameters.