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Keywords:

  • sputtering;
  • aluminium nitride;
  • passivation;
  • antireflective coating

Abstract

High bandgap materials have recently attracted a lot of interest for their potential application in photovoltaics (PV). Aluminium nitride (AlNx) is a potential candidate for the passivation and antireflective coating on silicon solar cells. AlNx thin films have been deposited by a remote plasma deposition system HiTUS (High Target Utilisation Sputtering). The AlNx thin films were grown by reactive sputtering from an aluminium target in a N2 atmosphere, negating the use of silane gas commonly used in PECVD deposition. PC1D simulations have been performed to calculate the best thickness for an antireflective coating for silicon wafers. Several depositions have been performed at different substrate temperatures. Photo conductive measurements by a WCT-100 were performed on silicon wafer after each thermal process to measure the effective minority carrier lifetime of p-type crystalline silicon wafer boron doped 〈100〉. Reflectance measurements were performed for samples prepared at different bias and flow gas ratios. Results show that the coating provides reflection reduction to levels below 5% for samples with a thickness of 70 nm. An increase in carrier lifetime has been observed for AlN deposited at high temperature. Annealing at 400 °C has been shown to increase carrier lifetime to 12 µs compared to 7 µs, suggesting the potential of AlN for silicon passivation and an alternative antireflective coating (ARC) to silicon nitride. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)