Design of the layer structures for Schottky type AlGaN UV photodetector

Abstract

Schottky-type UV photodetectors with three AlGaN layer structures were designed, simulated and investigated to develope a best performing UV photodetector by inserting a low temperature ultrathin AlGaN interlayer between the active AlGaN and GaN layers. Compared to the direct growth of AlGaN layer on GaN buffer, layer structures with an AlGaN interlayer showed an improved crystal quality resulting in a sharper Raman E2 phonon mode, reduced reverse leakage currents and better photo responsivity with an UV/visible rejection ratio of 4.7 × 104 and a cutoff wavelegth of 290 nm. The experimental results proved that the introduction of an AlGaN interlayer is important for the quality enhancement of active AlGaN surfaces resulting in an improved UV/visible rejection ratio and sharper change of photo responsivity. Further optimisation of the AlGaN photo detectors would be possible by inserting a highly doped AlGaN layer as well as ultrathin AlGaN interlayer in a limited overall thickness to avoid surface cracks. © 2003 WILEY-VCH Verlag GmbH & Co. KGaA.