Study of the Surface Photovoltage and Photovoltaic Properties of Au/δ-GaN/n-GaAs Schottky Barrier-Based Photodetectors

This work focuses on the photoelectrical and photovoltaic characteristics of Au/δ-GaN/n-GaAs Schottky barrier diodes (SBDs), aiming to evaluate the influence of an ultra-thin GaN interlayer on their performance. The devices were experimentally fabricated and examined through current–voltage (I–V) measurements under both dark and illuminated conditions, while complementary numerical simulations were employed to gain deeper insight into their behavior. The fabricated structure exhibited good electrical quality, attributed to the GaN interlayer, with a reduced ideality factor of 1.15 and an increased Schottky barrier height of 0.81 eV. Under illumination, the device exhibits a strong wavelength-dependent photoresponse, with optimal performance in the UV-visible range (200–400 nm), as confirmed by enhanced photocurrent generation and surface photovoltage (SPV) measurements. The extracted excess carrier concentration (δn) and interface state density (Nss) indicate that the GaN interlayer effectively passivates interface defects, minimizing recombination losses, and improving carrier collection. In addition, photovoltaic measurements indicate a pronounced short-circuit current density (Jsc) and open-circuit voltage (Voc) at shorter wavelengths, accompanied by a consistently stable fill factor (FF) across the different wavelengths. These results highlight the device’s effectiveness in converting optical energy into electrical power. These findings contribute to the advancement of GaN/GaAs heterostructures for high-performance photodetectors and energy harvesting applications, emphasizing the crucial role of interface engineering in optimizing optoelectronic device performance.