Journal of Luminescence, vol.257, 2023 (SCI-Expanded)
© 2023 Elsevier B.V.Temperature-dependent photoluminescence (PL) and surface photovoltage (SPV) measurements were carried out to detect radiative and non-radiative transitions on InGaN/GaN quantum well (QW) blue light-emitting device (LED). The emissions, peaking at 3.03 eV and 2.89 eV, were present in both PL and SPV spectrum and shifted with the temperature in a decrease-increase-decrease manner; the so-called S-shaped behavior between 30-150 K. Remarkably, the shift continued with an increase in energy (blue shift) and finally saturated for a temperature above 150 K. The first variation below 150 K was explained by the composition fluctuation of In atom in the InGaN MQW layer. In contrast, the second significant shift in peak energy was caused to the localization effect, around 60 meV. The degree of localized (σ) value agreed with the activation energy of thermal quenching of PL intensity. A strong localization effect was also attributed to the sub-bandgap trap level in the quantum well and originated negative capacitance in admittance spectroscopy measurement.