Temperature-dependent charge transport and double gaussian barrier inhomogeneity in Au/PDI/n-Ge schottky diodes

An Au/PDI/n-Ge Schottky diode with a perylene diimide (PDI) organic interlayer was fabricated and its electrical behavior was investigated over the temperature range of 100–350 K. AFM analysis revealed a continuous yet non-uniform surface with nanoscale island-like features, indicating interfacial inhomogeneity. Temperature-dependent I–V characteristics exhibited strong rectification, while the barrier height increased and the ideality factor decreased with temperature, clearly deviating from ideal thermionic emission (TE). This deviation was rigorously analyzed using a double Gaussian distribution (GD) model, revealing two distinct barrier regimes associated with localized low-barrier patches embedded in a higher background barrier, consistent with inhomogeneous Schottky interfaces. The extracted mean barrier heights (~ 0.59 eV and ~ 1.004 eV) confirm spatial barrier fluctuations governing carrier transport. Modified Richardson analysis yielded values close to the theoretical constant, validating the GD-assisted TE model. Current transport analysis demonstrated a transition from ohmic conduction to trap-controlled and trap-free space-charge-limited current (SCLC), while reverse bias behavior was dominated by Schottky emission. Interface state density ( Nₛₛ ) was found to decrease significantly with increasing temperature, indicating thermally activated passivation of interface traps. These results provide compelling evidence that charge transport in the Au/PDI/n-Ge diode is governed by Gaussian-distributed barrier inhomogeneity and interface states, highlighting the critical role of the PDI interlayer in tuning interfacial energetics and enhancing device performance.