Modulating Carrier Distribution for Efficient AlGaN-Based Deep Ultraviolet Light-Emitting Diodes by Introducing an Asymmetric Quantum Well

Abstract

Owing to poor hole-injection efficiency, conventional AlGaN-based deep-ultraviolet (DUV) light-emitting diodes (LEDs) generally suffer from a seriously inhomogeneous carrier distribution in the quantum well region. This leads to uneven radiative recombination rates, seriously affecting the luminous efficiency. In this paper, however, we propose an asymmetric quantum well (AQW) near the interface between the last quantum barrier and the electron blocking layer to fully utilize the inhomogeneous distribution characteristics. The optoelectronic performances of conventional and a proposed DUV-LED with an AQW have been numerically simulated and analyzed. The results reveal that electrons and holes tend to gather and recombine in the AQW region. This significantly enhances the internal quantum efficiency and the light output power with an improvement of about 120%, although it increases the peak emission wavelength red-shift. The peak emission wavelength of the AQW can be adjusted to the wavelength of the original structure while keeping a high optical efficiency by simply increasing the Al composition.

A Review of Recent Research Advances on AlGaN-Based Deep Ultraviolet Light-Emitting Diodes

“…Compared with the reference structure, the AlGaN-based DUV-LEDs with the BSB structure exhibit a 147% improvement in carrier radiation compounding efficiency and have an IQE of 78.75%. In addition to improving the carrier radiative compounding efficiency by improving the uniformity of carrier distribution in MQWs, the inhomogeneity of carrier distribution can also be utilized to improve the carrier radiative compounding efficiency, which in turn improves the luminous efficiency of AlGaN-based DUV-LEDs.Wang et al [87] introduced asymmetric quantum wells (AQWs) between the interface between the last quantum barrier and the electron-blocking layer in order to fully utilize the property of uneven carrier distribution, as shown in Figure 27. Since the AQWs is formed by the Al component of the last quantum barrier being a stepwise asymptotic decrease, a carrier aggregation region is formed at the last quantum barrier, where the electrons and holes are reaggregated and complexed.…”

Performance of Improvement of AlGaN‐Based Deep UV Light‐Emitting Diode with Two Parts Linearly Graded Barriers

“…[ 36 ] In addition, the polarization charge density is set at 0.4. [ 37 ] Other simulation parameters used in this work have been published in Vulgaftman's related articles. [ 38 ]…”

Evaluating the performance of an AlGaN based deep ultraviolet laser diode using graded waveguide layer and graded cladding layer

“…Especially, the optical confinement factor (OCF) has a significant impact. After the optimization of AlGaN p-CL, the threshold current density becomes very low [16], and the quantum confinement Stark effect of the active region is reduced, thus providing better optical confinement [31][32][33]. Due to the large exciton binding energy in type III nitride-based multiple quantum wells (MQWs), the exciton recombination process is expected to play a major role in the band-edge optical transition even at room temperature [34,35].…”