Electrical, optical and materials properties of ion beam synthesised (IBS) FeSi 2

Abstract

The electrical and optical properties of FeSi 2 structures produced by ion beam synthesis (IBS) are investigated. Above 150 K both α and β FeSi 2 n-Si structures display good Schottky diode characteristics. β FeSi 2 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 α FeSi 2 n-Si for the same diode area, is an order to magnitude higher than that for the β FeSi 2 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 βFeSi 2, is produced, the photoluminescence (PL) signal is indistinguishable from the background noise at 80 K. However, for lower dose samples (in the dose range 5 × 10 15−1 × 10 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 Å at the surface and smaller precipitates <50 Å in diameter around the projected range of the implant. For even lower dose samples (1 × 10 14 Fe cm −2) no PL signal is observed which correlates to the lack of βFeSi 2 precipitates in the XTEM micrographs.