Enhancing Efficiency of AlGaN Ultraviolet‐B Light‐Emitting Diodes with Graded p‐AlGaN Hole Injection Layer

Abstract

Ultraviolet‐B (UVB) AlGaN light‐emitting diodes (LEDs) with a hybrid hole injection layer comprising a 5 nm thin p‐AlxGa(1−x)N linearly graded layer (LGL), x from 0.65 to 0.50, and a 15 nm conventional p‐AlGaN layer are proposed for ≈284 nm wavelength emission. The introduced p‐AlxGa(1−x)N LGL effectively improves the confinement of the electrons in the active region by effectively increasing the conduction band barrier height. Moreover, it enhances the hole injection capability into the active region by energizing the holes that minimize the effective valence band barrier height. As a result, the proposed LED structure exhibits an incredibly reduced electron leakage, ten times lower than that of the conventional structure. Moreover, the output power and electroluminescence intensity of the proposed structure are enhanced by approximately twice at 60 mA current injection. Thus, the LGL LED structure can be a potential candidate for high‐power UV light emitters.

Enhanced performance of AlGaN-based deep-UV LED by incorporating carrier injection balanced modulation layer synergistically with polarization-regulating structures

“…The electrostatic field of LED-3 is lower at the EBL/p-AlGaN and the p-AlGaN/p-GaN interfaces than those in LED-1 and LED-2. This indicates the weakened electric field enables more holes to be injected and transported in the active region [27]. At the same time, a slight decrease of the electrostatic field in the MQWs is also observed, for which the carrier confinement is improved in LED-3.…”

Deep-ultraviolet LEDs with an Al-graded p-AlGaN layer exhibiting high wall-plug efficiency and high modulation bandwidth simultaneously

“…In addition, using p-AlGaN with graded Al composition as the p-type contact layer can also improve the bandwidth of the LED. It is reported to reduce the polarization between the last QW and the electron barrier, improve the hole injection efficiency and enhance the radiative recombination rate [32][33][34]. These reports also showed changes in the carrier concentration in the active region after using a p-AlGaN contact layer with graded Al composition.…”

“…In addition, Zhang et al [30] proved that the AlGaN layer with a graded decrease of Al component can induce three-dimensional hole gas, thus greatly increasing the hole concentration. Many papers have also demonstrated by simulation that the p-AlGaN contact layer with graded Al components can improve the LED hole injection efficiency and reduce the hole barrier [31][32][33][34]. This further demonstrates the superiority of Al component gradient AlGaN as a p-type contact layer.…”

Highly Stable White Light Emission from III-Nitride Nanowire LEDs Utilizing Nanostructured Alumina-Doped Mn4+ and Mg2+

“…Nanostructured III-nitride materials have attracted significant attention due to their great potential applications in micro-displays, conformable light sources, and augment/virtual reality technology. The light-emitting diodes (LEDs) that could emit different wavelengths from ultraviolet (UV), visible light, and infrared (IR) by controlling the In, Ga, and Al composition in In­(Al)­GaN materials are intensively investigated. − However, the fabrication of high-efficiency full-color LEDs, especially at long wavelengths (green and red light), remains a challenge that hinders the commercial availability of micro-displays. − In addition, luminous efficacy of the LEDs can attain 50 to 70% of the theoretical maximum . More than 30% of the energy is converted into heat which reduces the LED luminescent efficacy and lifetime.…”