Characteristics of front-illuminated visible-blind UV photodetector based on GaN p-i-n photodiodes with high quantum efficiency

Abstract

In this work, we reported the fabrication and characterization of an Al x Ga 1-x N /GaN hetero-epitaxial front-illuminated visible-blind UV photodetector with very high external quantum efficiency. This device was grown on one side of polished sapphire substrate using a low-temperature AlN buffer layer created by three-pocket multi-wafer system metalorganic chemical vapor deposition (MOCVD) with a vertical reactor. This device consisted of a 2.5μm thick GaN n-layer, a 0.4μm thick GaN i-layer and Al 0.1 Ga 0.9 N window layer, followed by a 10 nm GaN:Mg p+ contact layer. In order to investigate the effect of p- Al 0.1 Ga 0.9 N thickness on the characteristics of the photodetector, three samples only with different p-AlGaN thicknesses of 0.1μm and 0.15μm were fabricated. All of the device processing was completed using standard semiconductor processing techniques that included photolithography, metallization and etching. Compared the results of these three samples, the sample with 0.15μm thick p-AlGaN possesses the highest quantum efficiency and its zero-bias peak responsivity was found around 0.20A/W at 365 nm, corresponding to an external quantum efficiency of 85.6%. Moreover, this device exhibits a low dark current density of 3.16nA/cm 2 at zero-bias.