Electrical, optical and materials properties of ion beam synthesised (IBS) FeSi2

The electrical and optical properties of FeSi2 structures produced by ion beam synthesis (IBS) are investigated. Above 150 K both alpha and beta FeSi2/n-Si structures display good Schottky diode characteristics. beta FeSi2/n-Si exhibits a low reverse leakage current up to - 20 V after which abrupt avalanche breakdown occurs. As expected, the reverse leakage current of alpha FeSi2/n-Si for the same diode area, is an order to magnitude higher than that for the beta FeSi2/n-Si diodes and the breakdown is less abrupt. The characteristics of both types of diode suggest that thermionic emission is the main conduction mechanism across the barrier. For samples implanted with higher doses of Fe, where a continuous layer of beta FeSi2, is produced, the photoluminescence (PL) signal is indistinguishable from the background noise at 80 K. However, for lower dose samples (in the dose range 5x10(15)-1x10(17) Fe cm(-2)) although the peak position remains the same the signal intensity is significantly increased and is visible at 80 K. Cross-sectional transmission electron microscopy (XTEM) results from these samples show precipitates with diameters of 400-600 Angstrom at the surface and smaller precipitates < 50 Angstrom in diameter around the projected range of the implant. For even lower dose samples (1 x 10(14) Fe cm(-2)) no PL signal is observed which correlates to the lack of beta FeSi2 precipitates in the XTEM micrographs.