Investigation of Electrical Characteristics in Al/CdS-PVA/p-Si (MPS) Structures Using Impedance Spectroscopy Method

Abstract

The cadmium sulfide (CdS) nanopowders have been prepared by ball-milling method, and CdS-polyvinyl alcohol (PVA) nanocompound in the form of film has been deposited on a p-Si wafer as an interfacial layer by spin-coating method. The impedance characteristics of the fabricated Al/CdS-PVA/p-Si (metal-polymer-semiconductor)-type structures were studied in the frequency and voltage range of 5 kHz-5 MHz and ±1 V, respectively, by considering interface states (Dit) , series resistance (Rs) , and interfacial layer effects at 300 K. While the voltage and frequency dependence profiles of Dit were evaluated from the low-high frequency capacitance (CLF - CHF) and Hill-Coleman methods, Rs profiles were evaluated from the Nicollian and Brews method. Doping concentration atoms (NA) and barrier height [ΦB (capacitance-voltage ( C - V ))] values were also obtained from the reverse bias C-2 versus V plots for each frequency. While Dit and Rs values decrease with increasing frequency almost exponentially, ΦB (C - V) increases linearly. Therefore, both the measured capacitance (Cm) and conductance (Gm/ω) values were corrected to eliminate the Rs effect. The experimental results show that Rs value is more effective on the impedance measurements at high frequencies in the accumulation region, but Dit is effective at low frequencies in the depletion region. © 2016 IEEE.