Enhanced Performance of MSM UV Photodetectors by Molecular Modification of Gallium Nitride Using Porphyrin Organic Molecules

Abstract

In this brief, we present a novel surface modification process for gallium nitride (GaN) epitaxial films leading to enhanced ultraviolet (UV) photodetection. The adsorption of a layer of thiol-functionalized porphyrin-based organic molecules on the GaN surface has been carried out. The effect of surface modification was seen in the form of a significant reduction in the surface potential of GaN by ~250 mV and five-fold enhancement in the near-band-edge photoluminescence intensity, both indicating surface passivation of GaN. Consequently, reverse current for Nickel (Ni) Schottky contacts on molecularly modified GaN was decreased by 3 orders of magnitude, in dark at room temperature. Upon illumination by UV light, Ni/molecular layer/GaN interdigitated structures showed considerably improved photodetector (PD) characteristics such as responsivity for the visible-blind spectral region, photo-to-dark current ratio, and UV-to-visible rejection ratio. Such metal-molecular layer semiconductor device structures can be useful for the fabrication of more efficient GaN-based UV PDs, mitigating the adverse effects of electronic surface states in these materials.