Improving performance of light-emitting diodes using InGaN/GaN MQWs with varying trapezoidal bottom well width

Abstract

We report the optical performance of four InGaN/GaN multiple quantum well (MQW) blue LEDs with different bottom base widths- LED A. InGaN/GaN rectangular shaped quantum wells (QWs) with well width of 2 nm, LED B. InGaN graded QWs with trapezoidal bottom base width of 0.8 nm, LED C. trapezoidal QWs with bottom base width of 0.6-nm, and LED D. trapezoidal QWs with bottom base width of 0.5 nm- in terms of optical output power and efficiency droop. The introduction of trapezoidal QW facilitates to decrease the piezoelectric polarization field in the well of InGaN/GaN based LED structure. Such structures not only increase overlapping between electron and hole wave functions, but cause uniform carrier distribution among all quantum wells thereby increasing the radiative recombination rate. The proposed LED C shows the best performance in terms of lowest efficiency droop of 4.7% and highest optical power output of 226 mW as compared to the efficiency droop of 48.8% and output power of 70 mW at input current of 120 mA obtained from the conventional LED structure, LED A.