Analysis of interface states and series resistance for Al/PVA:n-CdS nanocomposite metal-semiconductor and metal-insulator-semiconductor diode structures

摘要

This paper presents the fabrication and characterization of Al/PVA:n-CdS (MS) and Al/Al_2O_3/PVA:n-CdS (MIS) diode. The effects of interfacial insulator layer, interface states (N_(ss)) and series resistance (R_s) on the electrical characteristics of Al/PVA:n-CdS structures have been investigated using forward and reverse bias Ⅰ-Ⅴ, C-Ⅴ, and G/w—Ⅴ characteristics at room temperature. Al/PVA:n-CdS diode is fabricated with and without insulator Al_2O_3 layer to explain the effect of insulator layer on main electrical parameters. The values of the ideality factor (n), series resistance (R_s) and barrier height (Φ_b) are calculated from ln(I) vs. V plots, by the Cheung and Norde methods. The energy density distribution profile of the interface states is obtained from the forward bias Ⅰ-Ⅴ data by taking into account the bias dependence ideality factor (n(Ⅴ)) and effective barrier height (Φ_e) for MS and MIS diode. The N_(ss) values increase from mid-gap energy of CdS to the bottom of the conductance band edge for both MS and MIS diode.