Low-damage wet chemical etching for GaN-based visible-blind p-i-n detector

Abstract

We have investigated wet chemical etching process of n⁺-type Al_0.33Ga_0.67N in 20% (by weight) aqueous KOH solutions at 106°C after Ar⁺ ion beam dry etching treatment. Scanning electron microscope and Auger electron spectroscopy were employed to characterize the surface morphology and stoichiometry with and without wet chemical etching. It is obvious that dry etching damages were reduced after wet chemical etching. We also fabricated two sets of visible-blind p-i-n detectors for comparison. I-V characterization indicated that the average leakage current of the wet etching treated detectors was lower than that of the detectors without treatment by about one order of magnitude. When the reverse bias was -5 V, the leakage currents of wet etching treated devices varied from -2.16×10^-9 to -6.26×10^-9 A and those of untreated detectors varied from -2.68×10^-8 to -3.49×10^-8 A. The peak responsivity at 365 nm was also tremendously enhanced by means of wet chemical etching treatment. It was 0.10 and 0.03 A/W under back illumination, with and without wet chemical treatment, respectively. When the detector was under front illumination, the result was 0.05 and 0.02 A/W, respectively.