Quantum-confined Stark effect on photoluminescence and electroluminescence characteristics of InGaN-based light-emitting diodes

The quantum-confined Stark effect (QCSE) on InGaN-based light-emitting diodes (LEDs) was investigated as a part of the continuing study of exploring differences between photoluminescence (PL) and electroluminescence (EL) characteristics. The luminescence characteristics were related to electrical characteristics of green and amber LEDs by employing the electrical-bias-applied PL technique. By inspecting the band diagram, it has been found that the separation of quasi-Fermi levels, which strongly affects the QCSE, can be quantified and related to the luminescence. In order to compare PL and EL characteristics, attention was paid to the QCSE during the PL and EL measurements. Despite the control of the QCSE, differences were still confirmed between PL and EL characteristics, which have led us to the conclusion to that there are other unrevealed origins for the differences.