Characterization of n-Type Nanocrystalline Iron Disilicide/Intrinsic Ultrananocrystalline Diamond/Amorphous Carbon Composite/p-Type Silicon Heterojunction Photodiodes

Abstract

We prepared n-type nanocrystalline iron disilicide (NC-FeSi2)/intrinsic (i) ultrananocrystalline diamond/amorphous carbon composite (UNCD/a-C)/p-type Si heterojunctions and evaluated as photodiodes. UNCD/a-C and NC-FeSi2 films were deposited by coaxial arc plasma deposition and pulsed laser deposition, respectively. The capacitance-voltage and current-voltage characteristics of heterojunctions were measured at room temperature. The inserted i-UNCD/a-C layer to form pin heterojunctions reduced the capacitance and dark current as compared with those in the case of pn heterojunctions. The build-in potential of heterojunctions was estimated to be 1.2 eV. The prepared heterojunctions showed typical rectifying action and a response for an illumination with a 6 mW, 1.31 μm laser. The recombination process is the predominant mechanism of current transport in the heterojunctions. The dynamic resistance area product and detectivity were 1.54 × 103 Ω cm2 and 5.0 × 108 cmHz1/2/W at-1 V. The evident improvement in the device performance was demonstrated, which should be due to the reduction of dark current by i-UNCD/a-C layer.