Broadband InGaAsP/InP NIR LEDs based on multiple photon-recycling photoluminescent layers

• Broadband NIR LEDs fabricated using a novel photoluminescent multilayer approach. • Wide emission spectra covering the entire NIR range. • High internal quantum efficiency and stable emission spectra. • Future work to optimize multilayer structure for enhanced performance. Infrared spectroscopy is a very popular measurement technique presently, especially in healthcare, agriculture, and food industry. NIR LEDs have high efficiencies, but narrow wavelengths, therefore they are suitable for measurements at a certain wavelength. GaInAsP/InP is an ideal material system for the fabrication of double heterostructure LED devices with tuneable emission wavelengths. The present study addresses the need when a broader emission-peak is preferred for spectroscopic applications. An LED structure is covered by photoluminescent layers grown epitaxially by liquid phase epitaxy. The primary light of the active layer excites the further layers which emit photoluminescent radiation. The partly transmitted primary and the secondary lights together result in a broader spectrum. This work presents NIR LEDs with wide emission spectra which cover the entire NIR range based on multiple photon-recycling photoluminescent layers. This type of NIR light source could replace the incandescent light sources on account of their small dimensions, high efficiency, and low power consumption, which is critical in small, handheld NIR spectroscopy devices.