A dual-character InGaN/GaN multiple quantum well device for electroluminescence and photovoltaic absorption of near-mutually exclusive wavelengths

Abstract

We report on the dual-character of an InGaN/GaN multiple quantum well (MQW) device structure epitaxially grown by MOCVD on a 150 mm Si-on-insulator (SOI) wafer. The fabricated mesa device exhibits photovoltaic (PV) response mainly for λ < 500 nm and strong electroluminescence (EL) for 470 nm < λ < 750 nm with a major amber component about 580 nm < λ < 620 nm. Multiple, high amplitude oscillations are observed in the luminescence spectra and verified by theoretical modelling as strong Fabry-Perot interference effects. HR-XRD ω -2θ (0002) scan estimates a mean In composition of ∼22% in the MQWs, consistent with the PV absorption edge and weak photoluminescence (PL) emission when excited by a 518 nm laser at 20K. Under 405 nm laser excitation at low temperatures, PL emission for 600 nm < λ < 740 nm is greatly enhanced. Asymmetric broadening of the spectral peak to 570 nm < λ < 740 nm occurs when the excitation energy is increased with a 325 nm laser, and is attributed to radiative transitions associated with MQW interface defects. This is supported by the (105) reciprocal space map which shows slight relaxation of the MQWs. The strong but broad long-wavelength emission, is ascribed to the MQW interface defects and highly recombinative In-rich clusters. These hardly contribute to PV response and are responsible for the protracted Stokes shift that constitutes the apparent near-mutual exclusion of EL and PV absorption wavelengths. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.