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1. Enhancing the light extraction efficiency of AlInN nanowire ultraviolet light-emitting diodes with photonic crystal structures

   https://doi.org/10.1364/OE.396788  

   Jain, Barsha; Velpula, Ravi_Teja; Tumuna, Moses; Bui, Ha_Quoc_Thang; Jude, Jeffrey; Pham, Thi_Tan; le, Thang_van; Hoang, Anh_Viet; Wang, Renjie; Nguyen, Hieu_Pham_Trung (July 2020, Optics Express)

   In this paper, AlInN nanowire ultraviolet light-emitting diodes (LEDs) with emission at ∼299 nm have been successfully demonstrated. We have further studied the light extraction properties of these nanowire LEDs using photonic crystal structures with square and hexagonal lattices of nanowires. The light extraction efficiency (LEE) of the periodic nanowire LED arrays was found to be significantly increased as compared to random nanowire LEDs. The LEEs reach ∼ 56%, and ∼ 63% for the square and hexagonal photonic crystal-based nanowire structures, respectively. Moreover, highly transverse-magnetic polarized emission was observed with dominant vertical light emission for the AlInN nanowire ultraviolet LEDs. 

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2. Study on the Quantum Efficiency Enhancement in AlInN Nanowire Light-Emitting Diodes Grown by Molecular Beam Epitaxy

   https://doi.org/10.1109/CSW55288.2022.9930404  

   Velpula, Ravi Teja; Jain, Barsha; Nguyen, Hieu P. (June 2022, 2022 Compound Semiconductor Week)

   We report on the demonstration of electron blocking layer free AlInN nanowire light-emitting diodes (LEDs) operating in the 280–365 nm wavelength region. The molecular beam epitaxial grown AlInN nanowires have a relatively high internal quantum efficiency of > 52%. Moreover, we show that the light extraction efficiency of the nanowires could reach ~ 63% for hexagonal photonic crystal nanowire structures which is significantly higher compared to that of the random nanowire arrays. This study provides significant insights into the design and fabrication of a new type of high-performance AlInN nanowire ultraviolet light-emitters. 

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3. Polarization-induced doping in AlInN/GaN nanowire ultraviolet light-emitting diodes

   https://doi.org/10.1117/1.JNP.19.042203  

   Das, Samadrita; Muthu, Mano_Bala Sankar; Nguyen, Pham_Thi_Thuy Lieu; Lenka, Trupti Ranjan; Talukdar, Fazal Ahmed; Nguyen, Hieu_Pham Trung (October 2025, Journal of Nanophotonics)

   We present our study on AlInN-based ultraviolet (UV) core-shell nanowire light-emitting diodes (LEDs) utilizing a polarization-induced doping technique. Due to the formation of a core-shell structure, the non-radiative recombination on the nanowire surface is significantly reduced. Moreover, we have successfully fabricated AlInN/GaN-based core-shell nanowire UV LED employing polarization-engineered quantum barriers instead of conventional structures. The LED device exhibits significantly improved carrier concentration in the active region and decreased electron leakage due to the gradually raised effective conduction band barrier heights. At room temperature, the AlInN LEDs exhibit strong and stable emission at 296 nm. We provide a promising approach to fabricating high-performance light emitters. 

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4. Numerical investigation on the device performance of electron blocking layer free AlInN nanowire deep ultraviolet light-emitting diodes

   https://doi.org/10.1364/OME.380409  

   Velpula, Ravi_Teja; Jain, Barsha; Bui, Ha_Quoc_Thang; Pham, Tan_Thi; Le, Van_Thang; Nguyen, Hoang-Duy; Lenka, Trupti_Ranjan; Nguyen, Hieu_Pham_Trung (January 2020, Optical Materials Express)

   We report on the illustration of the first electron blocking layer (EBL) free AlInN nanowire light-emitting diodes (LEDs) operating in the deep ultraviolet (DUV) wavelength region (sub-250 nm). We have systematically analyzed the results using APSYS software and compared with simulated AlGaN nanowire DUV LEDs. From the simulation results, significant efficiency droop was observed in AlGaN based devices, attributed to the significant electron leakage. However, compared to AlGaN nanowire DUV LEDs at similar emission wavelength, the proposed single quantum well (SQW) AlInN based light-emitters offer higher internal quantum efficiency without droop up to current density of 1500 A/cm²and high output optical power. Moreover, we find that transverse magnetic polarized emission is ∼ 5 orders stronger than transverse electric polarized emission at 238 nm wavelength. Further research shows that the performance of the AlInN DUV nanowire LEDs decreases with multiple QWs in the active region due to the presence of the non-uniform carrier distribution in the active region. This study provides important insights on the design of new type of high performance AlInN nanowire DUV LEDs, by replacing currently used AlGaN semiconductors. 

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5. High-performance nanowire ultraviolet light-emitting diodes with potassium hydroxide and ammonium sulfide surface passivation

   https://doi.org/10.1364/AO.400877  

   Bui, Ha_Quoc_Thang; Velpula, Ravi_Teja; Jian, Barsha; Philip, Moab_Rajan; Tong, Hien_Duy; Lenka, Trupti_Rajan; Nguyen, Hieu_Pham_Trung (August 2020, Applied Optics)

   Potassium hydroxide (KOH) and ammonium sulfide $({\mathrm{N}\mathrm{H}}_4{)}_2{\mathrm{S}}_x$have been used as a surface passivation treatment to improve the electrical and optical performance of AlGaN nanowire ultraviolet (UV) light-emitting diodes (LEDs). Enhancements in photoluminescence at 335 nm (49%), optical output power (65%), and electroluminescence (83%), with respect to the as-grown nanowire LED are recorded for the AlGaN nanowire UV LEDs with surface passivation. These enhancements are attributed to the reduced nonradiative recombination on the nanowire surfaces. This study provides a potential surface passivation approach to produce high-power AlGaN nanowire LEDs operating in the UV spectrum. 

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