Achieving 9.6% efficiency in 304 nm p-AlGaN UVB LED via increasing the holes injection and light reflectance

Abstract

Crystal growth of eco-friendly, ultrawide bandgap aluminium gallium nitride (AlGaN) semiconductor-based ultraviolet-B (UVB) light-emitting diodes (LEDs) hold the potential to replace toxic mercury-based ultraviolet lamps. One of the major drawbacks in the utilisation of AlGaN-based UVB LEDs is their low efficiency of about 6.5%. The study investigates the influence of Al-graded p-type multi-quantum-barrier electron-blocking-layer (Al-grad p-MQB EBL) and Al-graded p-AlGaN hole source layer (HSL) on the generation and injection of 3D holes in the active region. Using the new UVB LED design, a significant improvement in the experimental efficiency and light output power of about 8.2% and 36 mW is noticed. This is accomplished by the transparent nature of Al-graded Mg-doped p-AlGaN HSL for 3D holes generation and p-MQB EBL structure for holes transport toward multi-quantum-wells via intra-band tunnelling. Based on both the numerical and experimental studies, the influence of sub-nanometre scale Ni film deposited underneath the 200 nm-thick Al-film p-electrode on the optical reflectance in UVB LED is investigated. A remarkable improvement in the efficiency of up to 9.6% and light output power of 40 mW, even in the absence of standard package, flip-chip, and resin-like lenses, is achieved on bare-wafer under continuous-wave operation at room temperature. The enhanced performance is attributed to the use of Al-graded p-MQB EBL coupled with softly polarised p-AlGaN HSL and the highly reflective 0.4 nm-thick Ni and 200 nm-thick Al p-electrode in the UVB LED. This research study provides a new avenue to improve the performance of high-power p-AlGaN-based UVB LEDs and other optoelectronic devices in III–V semiconductors.

Exploring the Replacement of Toxic Mercury UV Lamp using AlGaN Tunnel Junction in 254 nm-Band DUV LED

“…Research and development of e cient AlGaN-based DUV LED at 254 nm emission wavelength is the safe and effective replacement of toxic Hg DUV lamp. Carrier con nement and transport issues in the MQWs are quite critical [44,45]. To resolve these issues of carrier con nement and transport, we provided a short roadmap for experimental efforts to realize internal quantum e ciency (IQE) beyond 70% in the AlGaN-TJ base DUV LEDs.…”

Reliability Analysis of AlGaN-Based Deep UV-LEDs

“…Muhammad Ajmal et al investigated the effect of Al-graded p-type MQB EBL and Al-graded p-AlGaN hole source layer (HSL) on the production and injection of 3D holes in the active region [ 24 ]. Their design provided a substantial improvement in the efficiency and light output power of about 8.2% and 36 mW respectively.…”

“… Schematic diagram of 304 nm-band AlGaN-based UVB-LED. [ 24 ] Copyright 2022, Springer Nature Publishing. …”

Study of AlGaN-based deep ultraviolet laser diodes using one-way step-shaped quantum barriers and symmetrical step-shaped electron and hole blocking layers

“…Due to the rapid development of III-nitride semiconductor materials and devices, the application of semiconductor light-emitting devices that operate in the deep ultraviolet band continues to expand, and they are widely used for pollution control, high-density information storage, lithography and disinfection. [1][2][3][4][5] In addition, deep ultraviolet laser diodes (DUV-LDs) have been extensively studied and applied because of their small size, light weight, and high-level reliability. 6,7 However, due to the lattice mismatch and polarization of the electric field, the device still contains serious amounts of carrier leakage along with its weak carrier confinement capabilities and low output power.…”