AlGaN-delta-GaN quantum well (QW) structures have been demonstrated to be good candidates for the realization of high-efficiency deep-ultraviolet (DUV) light-emitting diodes (LEDs). However, such heterostructures are still not fully understood. This study focuses on investigation of the optical properties and efficiency of the AlGaN-delta-GaN QW structures using self-consistent six-band k⸱p modelling and finite difference time domain (FDTD) simulations. Structures with different Al contents in the AlxGa1−xN sub-QW and AlyGa1−yN barrier regions are examined in detail. Results show that the emission wavelength () can be engineered through manipulation of delta-GaN layer thickness, sub-QW Al content (x), and barrier Al content (y), while maintaining a large spontaneous emission rate corresponding to around 90% radiative recombination efficiency (ηRAD). In addition, due to the dominant transverse-electric (TE)-polarized emission from the AlGaN-delta-GaN QW structure, the light extraction efficiency (ηEXT) is greatly enhanced when compared to a conventional AlGaN QW. Combined with the large ηRAD, this leads to the significant enhancement of external quantum efficiency (ηEQE), indicating that AlGaN-delta-GaN structures could be a promising solution for high-efficiency DUV LEDs.

We report on the realization of top-down fabricated, electrically driven, deep-ultraviolet (DUV) AlGaN micropillar array light emitting diodes (LEDs) with high output power density. Ordered arrays of micropillars with the inverse-taper profile were formed from an AlGaN epitaxial stack (epistack) using a Ni-masked Cl2 plasma dry etch and KOH-based wet etching. Following deposition of the n-contact, polydimethylsiloxane was spin-coated and etched-back to reveal the tips of the pillars to allow for formation of the p-contact. The DUV LEDs were tested at the wafer-level using a manual probe station to characterize their electrical and optical properties, revealing stable electroluminescence at 286 nm with a narrow 9-nm linewidth. Optical output power was found to be linearly related to current density, with output power densities up to 35 mW/cm2, comparable to the results reported for epitaxially grown DUV nanowire LEDs. Simulations revealed that the inverse-taper profile of the micropillars could lead to large enhancements in light extraction efficiency (ηEXT) of up to 250% when compared to micropillars with vertical sidewalls. The realization of ordered, electrically driven, top-down fabricated micropillar DUV LEDs with competitive output power represents an important step forward in the development of high-efficiency, scalable DUV emitters for a wide range of applications.

High-efficiency III-nitride deep-ultraviolet (DUV) lasers and light-emitting diodes (LEDs) with emission wavelengths of 240–260 nm are extremely difficult to realize due to large defect density from III-nitride materials and existence of optical polarization crossover from conventional AlGaN-based quantum wells (QWs). Free-standing wurtzite AlGaN templates have been studied and developed recently; however, the physics and optical properties of AlGaN-based emitters on AlGaN templates are still relatively lacking. Therefore, this work theoretically investigates the optical properties and quantum efficiencies of the AlGaN-based QW on AlGaN substrates. The physics analysis based on a self-consistent 6-band k⋅p model shows the transverse electric (TE)-polarized optical gain increases from 558 cm−1 by using Al0.51Ga0.49N/AlN QW on the AlN substrate to 2875 cm−1 by using Al0.48Ga0.52N/Al0.72Ga0.28N QW on the Al0.72Ga0.28N substrate at 260 nm, which is attributed to the reduced strain effect and valence band rearrangement by using the AlGaN substrate. Correspondingly, the radiative recombination efficiency increases 1.66–4.43 times based on different Shockley–Read–Hall coefficients, indicating the promising potential of the use of the AlGaN substrate for high-efficiency DUV lasers and LEDs.