Wavelength selective p-GaN/ZnO colloidal nanoparticle heterojunction photodiode

Abstract

An ultraviolet heterojunction photodiode consisting of epitaxially grown p-GaN layers and polyvinyl alcohol coated ZnO colloidal nanoparticles exhibits a lowpass and bandpass alternative property depending on the illumination direction. At 0 V bias, a time response on the order of 10 s of milliseconds was demonstrated with a responsivity on the order of mA/W with about 100 nW of ultraviolet illumination. The rectification ratio at ±5 V was 1000 under dark environment. Deposition of colloidal ZnO nanoparticles on an independent p-GaN substrate introduces a technique to create a heterostructure pn junction photodiode with wavelength selection by back illumination.