Electrical, optical and morphological properties of Au/n-Ge heterostructures by using cobalt phthalocyanine (CoPc) interlayer

The morphology of CoPc thin films on n-Ge substrate characterized using AFM measurements shows fairly smooth surface with RMS roughness of 8.42 nm. Structural analysis of cobalt phthalocyanine (CoPc) thin films is confirmed using Raman measurements at 785 nm excitation wavelength with three vibrational modes at 1539 cm⁻¹ resembles the C-N bond and 755 cm⁻¹, 685 cm⁻¹resembles to C-C bonds. The EDS spectrum of the Au/CoPc/n-Ge surface reveals the presence of elements contributing the structure of CoPc. Optical properties of CoPc thin films described with a Q band splitting between 600 to 700 nm with an optical bandgap of 3.8 eV The electrical measurements of Au/n-Ge Schottky heterostructures with CoPc interlayer reveals that the barrier height parameters are significantly improved than without interlayer. Low series resistance values of heterostructures than pristine contact shows its applicability in efficient photovoltaic cells. The conduction mechanisms of these contacts are evaluated using forward current-voltage properties. At moderately high forward voltages, the transport properties of Au/CoPc/n-Ge heterostructures are truly dominated by trap charge limited current (TCLC) mechanism. The photodiode properties of CoPc/n-Ge heterostructures were investigated at 775 nm wavelength and the responsivity and detectivity of the contacts found to be varied with reverse voltage.