Highly efficient transverse-electric-dominant ultraviolet-C emitters employing GaN multiple quantum disks in AlN nanowire matrix

Ram Chandra Subedi; Jung-Wook Min; Somak Mitra; Kuang-Hui Li; Idris Ajia; Edgars Stegenburgs; Dalaver H. Anjum; Michele Conroy; Kalani Moore; Ursel Bangert; Iman S. Roqan; Tien Khee Ng; Boon S. Ooi

doi:10.1117/12.2576596

5 March 2021 Highly efficient transverse-electric-dominant ultraviolet-C emitters employing GaN multiple quantum disks in AlN nanowire matrix

Ram Chandra Subedi, Jung-Wook Min, Somak Mitra, Kuang-Hui Li, Idris Ajia, Edgars Stegenburgs, Dalaver H. Anjum, Michele Conroy, Kalani Moore, Ursel Bangert, Iman S. Roqan, Tien Khee Ng, Boon S. Ooi

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Proceedings Volume 11686, Gallium Nitride Materials and Devices XVI; 1168610 (2021) https://doi.org/10.1117/12.2576596
Event: SPIE OPTO, 2021, Online Only

Abstract

Heavy reliance on extensively studied AlGaN based light emitting diodes (LEDs) to replace environmentally hazardous mercury based ultraviolet (UV) lamps is inevitable. However, external quantum efficiency (EQE) for AlGaN based deep UV emitters remains poor. Dislocation induced nonradiative recombination centers and poor electron-hole wavefunction overlap due to the large polarization field induced quantum confined stark effect (QCSE) in “Al” rich AlGaN are some of the key factors responsible for poor EQE. In addition, the transverse electric polarized light is extremely suppressed in “Al”-rich AlGaN quantum wells (QWs) because of the undesired crossing over among the light hole (LH), heavy hole (HH) and crystal-field split-off (SH) states. Here, optical and structural integrities of dislocation-free ultrathin GaN quantum disk (QDisk) (~ 1.2 nm) embedded in AlN barrier (~ 3 nm) grown employing plasma-assisted molecular beam epitaxy (PAMBE) are investigated considering it as a novel nanostructure to realize highly efficient TE polarized deep UV emitters. The structural and chemical integrities of thus grown QDisks are investigated by high angle annular dark field scanning transmission electron microscopy (HAADF-STEM). We, particularly, emphasize the polarization dependent photoluminescence (PL) study of the GaN Disks to accomplish almost purely TE polarized UV (~ 260 nm) light. In addition, we observed significantly high internal quantum efficiency (IQE) of ~ 80 %, which is attributed to the enhanced overlap of the electron-hole wavefunction in extremely quantum confined ultrathin GaN QDisks, thereby presenting GaN QDisks embedded in AlN nanowires as a practical pathway towards the efficient deep UV emitters.

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Ram Chandra Subedi, Jung-Wook Min, Somak Mitra, Kuang-Hui Li, Idris Ajia, Edgars Stegenburgs, Dalaver H. Anjum, Michele Conroy, Kalani Moore, Ursel Bangert, Iman S. Roqan, Tien Khee Ng, and Boon S. Ooi "Highly efficient transverse-electric-dominant ultraviolet-C emitters employing GaN multiple quantum disks in AlN nanowire matrix", Proc. SPIE 11686, Gallium Nitride Materials and Devices XVI, 1168610 (5 March 2021); https://doi.org/10.1117/12.2576596

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