Interface-state density estimation of n-type nanocrystalline FeSi₂/p-type Si heterojunctions fabricated by pulsed laser deposition

By utilizing pulsed laser deposition (PLD), heterojunctions comprised of n-type nanocrystalline (NC) FeSi₂/ thin films and p-type Si substrates were fabricated at room temperature in this study. Both dark and illuminated current density-voltage (J-V ) curves for the heterojunctions were measured and analyzed at room temperature. The heterojunctions demonstrated a large reverse leakage current as well as a weak near-infrared light response. Based on the analysis of the dark forward J-V curves, at the V value ≤ 0.2 V, we show that a carrier recombination process was governed at the heterojunction interface. When the V value was > 0.2 V, the probable mechanism of carrier transportation was a space-charge limitedcurrent process. Both the measurement and analysis for capacitance-voltage-frequency (C-V-f ) and conductance-voltage-frequency (G-V-f ) curves were performed in the applied frequency ( f ) range of 50 kHz-2 MHz at room temperature. From the C-V-f and G-V-f curves, the density of interface states (Nss) for the heterojunctions was computed by using the Hill-Coleman method. The Nss values were 9.19 × 10¹² eV^-1 cm^-2 at 2 MHz and 3.15 × 10¹⁴ eV^-1 cm^-2 at 50 kHz, which proved the existence of interface states at the heterojunction interface. These interface states are the probable cause of the degraded electrical performance in the heterojunctions.