Browsing by Author "Huang, Huamao"

Now showing 1 - 2 of 2

High Output Power GaN-Based Green Resonant-Cavity Light-Emitting Diodes With Trapezoidal Quantum Wells
(2020-09-01)
Wu, Haocheng
;
Li, Heng
;
Kuo, Shiou-Yi
;
Chen, Bo-Yan
;
Lu, Tien-Chang
Green resonant-cavity light-emitting diode (RCLED) has great potential in optical communication but suffers low efficiency. In this study, GaN-based flip-chip green RCLED incorporated with nitrogen face-oriented inclination asymmetric trapezoidal quantum wells (NOAT-QWs) is proposed to enhance the light-output power (LOP). Samples with NOAT-QWs and normal symmetric square quantum wells (SS-QWs) were fabricated and characterized. Although their electrical characteristics and emission spectra are similar, the LOP and emission efficiency are significantly improved. At a driving current of 450 mA, the improvement of LOP for RCLED with NOAT-QWs can be as high as 1.44 times in comparison to the sample with SS-QWs. The unprecedented high output power of 115 mW and the narrow full-width-at-half-maximum (FWHM) of 6.4 nm in the emission spectrum give great potential in optical communication. The inherent mechanism was investigated by the finite element analysis, from which the simulation results match well with the experimental measurements. The simulation results reveal that the NOAT-QWs are beneficial in alleviating the quantum confined stark effect and facilitating easier hole carriers' flow across the barriers, leading to more electron-hole wave function overlaps and higher radiative recombination rate.
Improved Performance of Near UV GaN-Based Light Emitting Diodes With Asymmetric Triangular Multiple Quantum Wells
(2019-02-01)
Li, Heng
;
Chang, Chia-Jui
;
Kuo, Shiou-Yi
;
Wu, Hao-Cheng
;
Huang, Huamao
Near-ultraviolet (NUV) light-emitting diodes (LEDs) have been used in several potential applications such as UV curing and biochemical sensors. However, the internal quantum efficiency (IQE) of NUV-LEDs is still a crucial issue. To improve the IQE, in this paper, an asymmetric triangular multiple quantum well (MQW) structure was used, which exhibited a higher emission efficiency and lower efficiency droop with nitrogen face-oriented inclination. This is in contrast to the trend observed in blue LEDs. Furthermore, we demonstrated that holes are more confined in MQWs with nitrogen face-oriented inclination than in MQWs with gallium face-oriented inclination. Moreover, simulations revealed that the IQE improved by approximately 32% compared with that of symmetric square MQWNUV-LEDs; this trend was also confirmed through experimental results. The external quantum efficiency of thin-film flip-chip LEDs with nitrogen face-oriented inclination MQWs was 52%.