Interface State Density and Series Resistance of n-Type Nanocrystalline FeSi₂/p-Type Si Heterojunctions Formed by Utilizing Facing-Target Direct-Current Sputtering.

Abstract

n-Type nanocrystalline FeSi2/p-type Si heterojunctions were formed by using facing-target direct- current sputtering at room temperature. The J-V characteristic results revealed that the reverse leakage current is large and the response under illumination of near-infrared light is very weak. The capacitance-voltage-frequency (C-V-f) and conductance-voltage-frequency (G-V-f) measurements were carried out at room temperature in order to estimate the series resistance (Rs) by using the Nicollian-Brews method and the density of interface state (Nss) by using the Hill-Coleman method. By estimation according to the Nicollian-Brews method, the Rs value increases with decreasing f value. The Rs values at zero bias voltage were 2.07 Ω at 60 kHz and 1.54 Ω at 2 MHz, which are consistent with those calculated by using the Cheung's and Norde's methods. The obtained Rs should be attributable to the Rs existing in the ohmic contact and neutral regions, which is the current-limiting factor for junctions. The nss values calculated by using the Hill-Coleman method were 2.70 × 1014 eV-1cm-2 at 60 kHz and 1.43 × 1013 eV-1cm-2 at 2 MHz. This result revealed the presence of interface states at the hetero-interface behaving as a leakage current center and a trap center of the photo-generated carrier, which degraded the junction properties at room temperature.