Analysis of efficiency droop in 280-nm AlGaN multiple-quantum-well light-emitting diodes based on carrier rate equation

Abstract

The efficiency droop in 280-nm AlGaN multiple-quantum-well (MQW) ultraviolet (UV) light-emitting diodes (LEDs) is analyzed using the carrier rate equation. It is shown that the internal quantum efficiency (ηIQE), injection efficiency (ηinj), light-extraction efficiency (ηLEE), Shockley–Read–Hall recombination coefficient (A), and Auger coefficient (C) can be determined by the carrier rate equation using the theoretical radiative recombination coefficient (B), experimentally measured wavelength spectrum, and external quantum efficiency (ηEQE). The results show that the carrier spillover from the MQWs to the p-AlGaN layer is the main cause of the efficiency droop.

Enhanced Radiative Recombination Rate by Local Potential Fluctuation in InGaN/AlGaN Near-Ultraviolet Light-Emitting Diodes

“…2019, 9, x FOR PEER REVIEW 7 of 12 case of identical epitaxial structure, the increase in the radiative recombination rate at low currents before the IQE peak was due to the decrease in defects (especially the point defects in the active MQW region) since the defects act as NRCs for carriers, inducing SRH recombination [30] as reflected in the A coefficient. Again, the calculated A coefficient [39] decreased with the sample's In composition (see Table 1), which is consistent with the PHEMOS patterns, nmin and S values at low currents. Thus, the effective radiative-recombination area increased with the reduction in point defects in QWs.…”

“…The IQE is defined as the ratio of the number of photons emitted from the active region per second to the number of electrons injected into the active region per second. The IQEs of NUV LED samples have been calculated by using the fitting method of calculating IQE as described in Reference [39], which is shown in Figure 6a. The LEEs of these samples have also been calculated by using Reference [39].…”

“…The IQEs of NUV LED samples have been calculated by using the fitting method of calculating IQE as described in Reference [39], which is shown in Figure 6a. The LEEs of these samples have also been calculated by using Reference [39]. Since LEE measures photon loss during propagation from the active region to free space [39], which is almost equal for all samples as seen in Figure 6b, the absorption of emitted photons by AlGaN barriers and GaN clad layers were similar for all samples [11].…”

“…The LEEs of these samples have also been calculated by using Reference [39]. Since LEE measures photon loss during propagation from the active region to free space [39], which is almost equal for all samples as seen in Figure 6b, the absorption of emitted photons by AlGaN barriers and GaN clad layers were similar for all samples [11]. For currents < 200 mA, the increase in IQE was caused by the increase in the radiative recombination rate, which is directly related to carrier localization and the effective radiative-recombination area in QWs.…”

The efficiency droop impact of GaN‐based LEDs on the performance of OFDM visible light communication system

“…However, the assumption of uniform carrier density in quantum wells (QWs) for this traditional rate equation model is not quite accurate. This is because that the effective light-emitting region can be greatly reduced by several reasons, such as quantum confinement effect, internal polarization filed, In composition fluctuation and poor hole injection [13][14][15][16][17]. In this work, the modified rate equation model for GaN-based LEDs is proposed by introducing effective recombination length and expressed as ( )…”