Optical characterisation of aluminium nitride as antireflective coating by a new remote plasma deposition system

High bandgap materials have recently attract a lot of interest for their potential application in photovoltaics (PV). Aluminium nitride (AlN)) is a potential candidate for passivation and antireflective coating in silicon solar cells. AlN thin films have been deposited by a new remote plasma deposition system HiTUS (High Target Utilisation Sputtering). The AlN thin films are grown by reactive sputtering from an aluminium target in an N(2) atmosphere, negating the use of silane gas commonly used in PECVD method. PC1D simulations have been performed to calculate the best thickness for antireflection and passivation of silicon wafers. Several depositions have been performed at different substrate temperatures. Photoconductive measurements by a WCT-100 were performed on silicon wafer after each thermal process to measure the effective lifetime of p-type crystalline silicon wafer boron doped < 100 > to measure the effective lifetime of the minority carriers. Reflectance and transmission measurements were performed for sample at different bias and flow gas ratio. Results shows that a complete transmission with a reflection of less than 5% occurs for samples with a thickness of 50 nm. An increase in carrier lifetime has been observed for AlN deposited at high temperature. Lifetime has increased in wafer annealed at 300 degrees C up to 15 mu s suggesting the potential of AlN for silicon passivation and an alternative antireflective coating to silicon nitride. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim