Photoconductivity in Porous GaN Layers

Abstract

The first observation of photoconductivity (PC) in porous GaN layers fabricated by surface anodization of 0.6 μm thick GaN layers grown by HVPE on 6H-SiC substrates is reported. PC was studied at room temperature and a strong photoresponse was observed in anodized GaN layers, whereas no photoconduction in initial (not anodized) epitaxial layers was detected. Both the buildup and the decay of the PC in anodized GaN demonstrated exponential behavior with two time constants of 1.8 and 100 s, respectively. PC spectra of anodized GaN showed a steady increase of the photoresponse as the photon energy was increased from 2.5 to 3 eV. Room and low temperature (15 K) photoluminescence studies were also performed on initial and anodized structures. EBIC measurements showed formation of a barrier on the GaN/SiC interface after anodization. Photoresponse in anodized GaN layers is ascribed to a decrease in carrier concentration in the anodized semiconductor.