Deep‐ultraviolet AlGaN light‐emitting diodes with variable quantum well and barrier widths

Abstract

In this study, a device scheme for improving the internal quantum efficiency (IQE) of AlGaN‐based deep‐ultraviolet light‐emitting diodes (DUV‐LEDs) is proposed and numerically investigated using SimuLED software. By step‐increasing the thickness of the quantum wells and step‐decreasing the thickness of quantum barriers in a multiple quantum well (MQW) structure, the IQE of a DUV‐LED at 20 mA is increased by a factor of approximately 1.3 relative to the reference LED. These improvements are attributed to increased radiative recombination rates resulting from enhanced hole injection and uniform carrier distribution within the MQWs.

Advantages of AlGaN-based deep ultraviolet light-emitting diodes with a superlattice electron blocking layer

“…In recent decades, high Al content Al x Ga 1Àx N-based deep ultraviolet light-emitting diodes (UV LEDs) have attracted significant attention due to their wide range of potential applications including air and water purification, germicidal and biomedical instrumentation systems, full color display, optical data storage, and white emission lighting [1][2][3][4]. However, low external quantum efficiency (EQE) http://dx.doi.org/10.1016/j.spmi.2015.05.010 0749-6036/Ó 2015 Elsevier Ltd. All rights reserved.…”

Design of electron blocking layers for improving internal quantum efficiency of InGaN/AlGaN-based ultraviolet light-emitting diodes

“…Figure 7 shows the IQE characteristics for the five structures. The reference structure shows a maximum of 52 % of IQE at the operation current density of 20 mA/cm 2 …”

“…Firstly, weak carrier confinement due to the shallow well and significant polarization field in both the active region and the EBL cause low radiative recombination in the active region. This results in low internal quantum efficiency [2]. Secondly, although EBLs with constant Al content are commonly used in UV LED structures, the related mechanisms are yet to be fully researched and explained.…”

On the Hole Injection for III-Nitride Based Deep Ultraviolet Light-Emitting Diodes

“…Tsai et al attribute the interesting observations to the reduced valence band offset for the Al x Ga 1− x N/Al y Ga 1− y N ( x < y ) based quantum wells, which therefore is beneficial for the hole transport across the MQW region [ 82 ], i.e., the valence band offset is 0.185 eV for the Al 0.55 Ga 0.45 N/Al 0.72 Ga 0.28 N quantum wells of Tsai et al and 0.210 eV for the In 0.15 Ga 0.85 N/GaN quantum wells with the ~450 nm emission wavelength [ 11 ], respectively. Till now, various conduction band offset/valence band offset ratios ( ΔE C / ΔE V ) are assumed when calculating the carrier transport within the Al x Ga 1− x N/Al y Ga 1− y N ( x < y ) based quantum wells, e.g., 70/30 [ 81 , 83 , 84 , 85 ], 65/35 [ 68 , 82 ] and 50/50 [ 24 , 72 ]. We agree to the point proposed by Tsai et al, since we find that the hole concentration in quantum well closest to the p-EBL becomes high if the ΔE C /ΔE V of 50/50 is adopted.…”

“…[ 86 , 87 , 88 , 89 ] employ the quantum barriers with the thickness smaller than 8 nm, and this is quite different from the InGaN/GaN based visible LEDs, which normally utilize the barrier thickness lager than 10 nm [ 11 ]. Kim et al then numerically propose that a thinner p-side quantum barrier thickness and a thicker n-side quantum barrier can further increase the hole concentration level in the quantum wells [ 85 ]. The findings by Kim et al are agreeable with the report by Tsai et al [ 82 ].…”