Piezoelectric effect on compensation of the quantum-confined Stark effect in InGaN/GaN multiple quantum wells based green light-emitting diodes

摘要

InGaN based light emitting diodes (LEDs) suffer from the adverse influence of band tilt due to the piezoelectric field induced quantum-confined Stark effect (QCSE). We demonstrate incremental recovering of QCSE induced band tilt along with its impact on the performance of III-nitride-based green LEDs (at 532.5 nm) by applying external stress. The external tensile stress determined by peak shift in Raman spectroscopy ranges from 0 to 0.95 GPa as the wafer curvature increases from 0 to 2.32 m(-1). Compared to the pristine LEDs wafer, the PL emission peak undergoes an increase in intensity of 61%, blue shift of 11.5 nm and peak narrowing of 5.5 nm through bending the wafer to the maximum curvature of 2.94 m(-1). These results all verify the adverse effects due to the presence of the QCSE effect in green LEDs, which can be effectively suppressed by the external tensile stress, thus improving both the radiative recombination rate and electron-hole wave function overlaps. Under optimal conditions, the light output power is enhanced by 12.4% in chips on epi-wafer (COW) form under the wafer to the maximum curvature of 2.94 m(-1) without affecting the voltage required to reach the same current density. This work sheds light on implementation of the facile design in real LEDs devices to achieve significant increase in light output without involving any complicated transferring process onto flexible substrates. (C) 2016 Elsevier Ltd. All rights reserved.