Perspectives on UVC LED: Its Progress and Application

Abstract

High-quality epitaxial layers are directly related to internal quantum efficiency. The methods used to design such epitaxial layers are reviewed in this article. The ultraviolet C (UVC) light-emitting diode (LED) epitaxial layer structure exhibits electron leakage; therefore, many research groups have proposed the design of blocking layers and carrier transportation to generate high electron–hole recombination rates. This also aids in increasing the internal quantum efficiency. The cap layer, p-GaN, exhibits high absorption in deep UV radiation; thus, a small thickness is usually chosen. Flip chip design is more popular for such devices in the UV band, and the main factors for consideration are light extraction and heat transportation. However, the choice of encapsulation materials is important, because unsuitable encapsulation materials will be degraded by ultraviolet light irradiation. A suitable package design can account for light extraction and heat transportation. Finally, an atomic layer deposition Al2O3 film has been proposed as a mesa passivation layer. It can provide a low reverse current leakage. Moreover, it can help increase the quantum efficiency, enhance the moisture resistance, and improve reliability. UVC LED applications can be used in sterilization, water purification, air purification, and medical and military fields.

The effectiveness of commercial household ultraviolet C germicidal devices in Thailand

“…With its nontoxicity, compactness, and instant turn-on compensation, the popularity of UVC-LED has been gradually rising. However, low external quantum efficiency, aging of the packaging material, and thermal management problems are the main faults 12 , 13 , 18 . A LED is a semiconductor light source that emits a particular wavelength of light depending on semiconductor material and its structure.…”

“…A LED is a semiconductor light source that emits a particular wavelength of light depending on semiconductor material and its structure. At the time, UVC-LED device is based on aluminum gallium nitride material with emission spectra of 200–280 nm 18 . The emission spectra of 3 studied LEDs were described in Table 1 .…”

Recent Advances in Packaging Technologies of AlGaN‐Based Deep Ultraviolet Light‐Emitting Diodes

“…AlGaN is the ternary alloy of GaN and AlN, whose bandgap could be adjusted from 3.4 to 6.2 eV, so as to fabricate UV LED devices covering full UV range. [ 17 ] Comparing with the conventional UV light sources, such as mercury lamps [ 9 ] , the AlGaN‐based UV LEDs have numerous advantages including energy saving, environment friendly, compact structure, longer lifetime, faster response, and mercury free. [ 21 ] Thus, UV LEDs are regarded as ideal substitute for the conventional UV mercury light sources which contain the toxic mercury and is banned by the Minamata Convention on Mercury.…”

“…Nevertheless, comparing with the mature epitaxial growth technologies of GaN‐based visible LEDs, there are still plenty of difficulties which should overcome before their wide applications, such as, poor internal quantum efficiency due to poor epitaxial growth crystal quality, low light extraction efficiency because of UV‐absorbing p‐contact and interface reflection loss etc. Therefore, a lot of methods have been proposed to deal with that, such as surface roughening, [ 12 ] photonic crystal, [ 13 ] patterned sapphire substrate (PSS), [ 14,15 ] arrays of truncated cone (TC)‐shaped active mesas coated, [ 16 ] atomic layer deposition (ALD), [ 17 ] and combining transparent contact layer and reflective electrode. [ 18,19 ] Although numerous efforts have been made in the epitaxial chip level of AlGaN‐based deep UV LEDs, the external quantum efficiency is still very low, the highest reported value is 20.3%, [ 18 ] which is far lower than that of blue LEDs (≈76%).…”

Device for Identifying the UV Emission Spectrum

“…The interest in the disinfection process and the development of new UV LEDs in this direction is an active research field, as shown in recent works [23][24][25][26][27][28][29][30][31].…”