Frequency-Dependent Capacitance and Conductance Characteristics of Ag/n-GaAs Schottky Diodes With a Perylene-Monoimide Organic Interlayer

A perylene-monoimide (PMI) organic semiconductor was used as a spin-coated interfacial layer in an Ag/PMI/n-GaAs/In Schottky diode fabricated on (100)-oriented n-type GaAs. The frequency-dependent capacitance–voltage (C–V) and conductance–voltage (G–V) characteristics were investigated at room temperature in the dark from 50 kHz to 1 MHz over the bias range −3 to +3 V. AFM analysis revealed a homogeneous PMI film with low surface roughness, indicating successful interface engineering and stable film formation on the n-GaAs surface. The C–V curves exhibited the inversion–depletion–accumulation behavior typical of MIS-type structures, confirming that the PMI layer modifies the Ag/n-GaAs contact into an organic-assisted MIS configuration. The series resistance extracted by the Nicollian–Brews method decreased systematically with increasing frequency, and the corrected admittance recovered the intrinsic MIS response. From the C⁻²–V analysis, the apparent barrier height rose from 1.41 eV at 50 kHz to 1.63 eV at 1 MHz, while the donor concentration remained at about 8 × 10¹⁵ cm⁻³. The frequency dispersion is attributed to the response of interface states at the PMI/n-GaAs boundary. The PMI interlayer therefore offers a promising route to interface engineering of high-frequency GaAs-based Schottky and optoelectronic devices.