Quality improvement of GaN on Si substrate for ultraviolet photodetector application

Abstract

GaN is grown on an Si substrate using metalorganic vapor-phase epitaxy. Compared with the full width at half maximum values from X-ray diffraction patterns and photoluminescence spectra of conventional GaN on the Si substrate, those of GaN on the Si substrate with the insertion of various-temperature AlN nucleation layers and Al0.3Ga0.7N/GaN superlattice intermediate layers are reduced by 34.9% and 25.6%, respectively. In addition, Raman spectra show that residual stress on the GaN epilayers decreased by 0.35 GPa. The c-lattice parameter of the GaN epilayer is 5.1844 Å, which is close to that of an unstrained GaN layer. Ultraviolet metal-semiconductor-metal photodetectors are fabricated on an almost-crack-free GaN surface. The dark current of a photodetector on the Si substrate is 2.4 × 10-11 A at a 9 V applied bias, which is one order of magnitude smaller than that of a photodetector on a conventional sapphire substrate. The maximum quantum efficiency value of a photodetector on the Si substrate is ~97% with an incident light wavelength of 360 nm and a 9 V applied bias. © 2013 IEEE.