Self-standing ZnO nanotube/SiO₂ core–shell arrays for high photon extraction efficiency in III-nitride emitter

Abstract

Self-standing ZnO nanotube (ZNT) arrays were fabricated on the surface of a GaN-based emitter with an indium tin oxide (ITO) transparent layer using a hydrothermal method and temperature cooling down process. For the greater enhancement of photon extraction efficiency, ZNT/SiO core-shell nanostructure arrays were fabricated on the emitter with a 430 nm wavelength. The optical output power of ZNT/SiO core-shell arrays on the emitter with ITO electrode was remarkably enhanced by 18.5%, 28.1%, and 55.9%, compared to those of ZNTs, ZNRs on an ITO film on an emitter and ITO film on an emitter as a conventional emitter, respectively. The large enhancement in optical output is attributable to the synergistic effect of efficient photon injection from the ITO/GaN layer to ZNTs because of the well-matched refractive indices and wave-guiding, in addition to the superior photon extraction by the SiO coating layer on the ZNTs.

Просветляющие покрытия на основе ZnO, полученные методом электронно-лучевого испарения

“…Поэтому для увеличения вывода света могут быть задействованы дополнительные операции обработки покрытия. Так, например, в работе [20] методом травления нанокристаллов ZnO вытянутой формы были получены нанотрубки, которые в последствии закрывались тонким слоем SiO 2 для увеличения просветляющего эффекта покрытия, а в работе [18] нанокристаллы ZnO покрывались сверху дополнительным наноструктурированным слоем NiO, уменьшающим контраст показателя преломления на границе ZnO−окружающая среда.…”

Ultraviolet Photoactivated Room Temperature NO2 Gas Sensor of ZnO Hemitubes and Nanotubes Covered with TiO2 Nanoparticles

“…In recent years, nanostructured semiconducting metal oxides such as SnO 2 , ZnO, TiO 2 , and CuO have been widely used to fabricate gas sensors because of their unique structure and surface-to-volume ratio compared to layered materials [4][5][6]. Among them, ZnO is largely utilized for the realization of various nanostructures, including nanorods (NRs), nanotubes (NTs), nanowires (NWs), nanowalls, and nanoflowers [7][8][9][10]. In particular, the different morphologies of ZnO NRs significantly affect the detection property of NO 2 gas sensors [11]; moreover, ZnO NRs-based sensors have a very low detection limit (10 ppm) for NO 2 gas at 250 • C, along with short response and recovery times [12].…”

“…Therefore, ZnO NTs are able to provide large sensitivity because of their large length-to-diameter ratio and surface-to-volume ratio than other nanostructures. There are several methods to realize ZnO NTs such as the temperature change etching process, wet chemical etching process, and removing some materials by heating [9,13,20]. We fabricated the ZnO tube shapes by ZnO deposition thickness on the polyvinylpyrrolidone (PVP) NWs and removing PVP NWs.…”

Self-Aligned Hierarchical ZnO Nanorod/NiO Nanosheet Arrays for High Photon Extraction Efficiency of GaN-Based Photonic Emitter

“…Different dimensions from zero to three-dimensional ZnO nanostructures have been synthesized using various precursors. These nanostructures are particularly important for realizing many applications, such as electronic devices, catalysis, and biomedical and sensing usage, especially, visible ultraviolet optical devices [6][7][8][9][10][11].…”

“…Recently, hierarchical and core-shell nanostructures that provide graded refractive index changes have been applied to achieve high PEE in photonic emitters [11,[21][22][23][24][25]. However, for the realization of hierarchical nanostructures, a separate seed layer deposition, high cost vacuum systems, and complicate fabrication processes are required [24,26,27].…”