Electrical, structural and photovoltaic properties of acceptor dye modified Au/n-Ge heterostructure

Abstract

n-Ge heterostructure is fabricated using organic dye interlayers such as sulforhodamine-G (SRG) using low-cost spin coating technique and explored its electrical and structural features. The I–V measurements of the Au/SRG/n-Ge heterostructure (HJ) show good rectification behavior. It has been noticed that the barrier height (0.73 eV) of the Au/SRG/n-Ge heterojunction was significantly higher than the Au/n-Ge Schottky diode (SD) (0.63 eV). Cheung's function and the Norde method has been utilized to evaluate the various barrier parameters to understand the non-ideal behavior of the contacts at higher bias region. The low value of the series resistance for HJ (53 Ω) is observed than compared to the SD without organic dye (2974 Ω). Barrier parameters evaluated from the Norde method were compared with those from the Cheung method and found that they confirmed the consistency of Schottky barrier parameters obtained from both techniques. The transport properties of the HJ and SD in the forward bias region are evaluated using the log (I) vs. log (V) plot. At larger forward bias voltages, a change in the drift of current conduction is observed from Ohmic current conduction to traps-assisted SCLC conduction. This may be ascribed to the presence of defects or traps at the n-Ge and SRG interface possibly associated with the organic dye. Also, the photovoltaic properties of the SRG/n-Ge heterostructures were evaluated at 100 mW/cm2 showing significant photoresponse indicates the usage of SRG dyes in photosensitive applications.