Monolithically integrated AlGaN/GaN/AlN-based solar-blind ultraviolet and near-infrared detectors

Abstract

Closely spaced, monolithically integrated photodetectors in two largely different wavelengths ranges are demonstrated. The device structure was grown by plasma-assisted molecular-beam epitaxy on an AlN-on-sapphire template, and it consists of a Si-doped AlGaN thin film, and a nearly strain compensated 40 period AlN/GaN superlattice with 1.0 nm-thick GaN quantum wells and 2.0 nm-thick AlN barriers. The entire structure is covered with an AlGaN cap. The superlattice constitutes the active region for the infrared detector, while the AlGaN buffer layer serves as active area for the ultraviolet detector. The photoconductive ultraviolet detector has a long wavelength cutoff at 250 nm, whereas the photovoltaic near-infrared detector has a centre wavelength of 1.37 µm.