Pt/AlGaN Schottky-Type UV Photodetector with 310nm Cutoff Wavelength

Abstract

Pt/AlGaN Schottky-type UV photodetectors were designed and fabricated. A low-temperature AlGaN interlayer buffer was grown between the AlGaN and GaN film in the diode structure epitaxy to obtain crack-free AlGaN active layers. A comparison was then made of the structural, electrical, and optical characteristics of two different diodes: one with an AlGaN(<TEX>$0.5\;{\mu}m$</TEX>)/n+-GaN(2 nm) structure (type 1) and the other with an AlGaN(<TEX>$0.5\;{\mu}m$</TEX>)/AlGaN interlayer(<TEX>$150\;{\AA}$</TEX>)/n+-GaN(<TEX>$3\;{\mu}m$</TEX>) structure(type 2). A crack-free AlGaN film was obtained by the insertion of a low-temperature AlGaN interlayer with an aluminum mole fraction of 26% into the <TEX>$Al_xGa_{1-x}N$</TEX> layer. The fabricated Pt/<TEX>$Al_{0.33}Ga_{0.67}N$</TEX> photodetector had a leakage current of 1 nA for the type 1 diode and <TEX>$0.1\;{\mu}A$</TEX> for the type 2 diode at a reverse bias of -5 V. For the photoresponse measurement, the type 2 diode exhibited a cut-off wavelength of 300 nm, prominent responsivity of 0.15 A/W at 280 nm, and UV-visible extinction ratio of <TEX>$1.5{\times}10^4$</TEX>. Accordingly, the Pt/<TEX>$Al_{0.33}Ga_{0.67}N$</TEX> Schottky-type ultraviolet photodetector with an AlGaN interlayer exhibited superior electrical and optical characteristics and improved UV detecting properties.