Intrinsic Infrared Luminescence from InGaN Epilayers

Abstract

The extension of nitride technology to longer wavelengths is a considerable technical challenge that poses fundamental questions about the origin of luminescence from semiconductor solid solutions. Among the commercial suppliers of nitride semiconductor devices, Nichia Company alone has fabricated amber InGaN LEDs which peak at 594 nm, while some of the present authors have reported 650 nm, red, photoluminescence (PL) from an epilayer of ‘high’ indium content. Here we show further that indium gallium nitride is capable of emitting not only red but also infrared radiation in a band-to-band process. By using a Stokes' shift model we predict a limiting peak, for intrinsic InGaN emission, near a wavelength of one micron, which is 0.7 eV lower in energy than the band gap of pure indium nitride. In confirmation of this prediction, we have measured intrinsic luminescence with peak wavelengths up to 950 nm in a selected InGaN epilayer.