THE STUDY OF Pd SCHOTTKY CONTACT ON POROUS GaN FOR UV METAL–SEMICONDUCTOR–METAL (MSM) PHOTODETECTORS

Abstract

High quality unintentionally doped n-type GaN layers were grown on Si (111) substrate using AlN (about 200 nm) as buffer layer by radio frequency (RF) nitrogen plasma-assisted molecular beam epitaxy (MBE). This paper presents the structural and optical studies of porous GaN sample compared to the corresponding as-grown GaN. Metal–semiconductor–metal (MSM) photodiode was fabricated on the samples. For as-grown GaN-based MSM, the detector shows a sharp cut-off wavelength at 362 nm, with a maximum responsivity of 0.254 A/W achieved at 360 nm. For porous GaN MSM detector, a sharp cut-off wavelength at 360 nm with a maximum responsivity of 0.655 A/W was achieved at 359 nm. Both the detectors show a little decrease in responsivity in the UV spectral region. The MSM photodiode based on porous GaN shows enhanced (2×) magnitude of responsivity relative to the as-grown GaN MSM photodiode. Enhancement of responsivity can be attributed to the relaxation of tensile stress and reduction of surface pit density in the porous sample.