Origins of the high-energy electroluminescence peaks in long-wavelength (∼495–685 nm) InGaN light-emitting diodes

Abstract

We investigate the unexpected high-energy electroluminescence (EL) peaks observed in long-wavelength InGaN light-emitting diodes (LEDs) with ground state emission peaks between ∼495 and 685 nm by studying the EL spectra of LEDs with varying quantum well (QW) thicknesses and indium compositions. In addition to the ground state emission, two high-energy emission peaks were observed in the LEDs with thick QWs and high indium compositions. The less energetic high-energy emission peak (2.4–2.6 eV) is attributed to the optical transitions involving excited states. Factors influencing the excited state transitions, such as the QW thickness and indium compositions, were also examined by simulations to better understand the occurrence of these transitions. The more energetic high-energy emission peak (2.8–3.1 eV) originates from V-defect sidewalls and was verified through micro-photoluminescence measurements. Identification of the high-energy emission peaks is essential as it enables targeted epitaxial or growth optimizations to minimize or eliminate these undesirable emission peaks. This work demonstrates the importance of using thin QWs to suppress the unwanted high-energy emissions due to excited state transitions and V-defect sidewalls for long-wavelength InGaN LEDs.