Journal of Physical Studies 25(1), Article 1701 [6 pages] (2021)
DOI: https://doi.org/10.30970/jps.25.1701

ULTRAVIOLET ELECTROLUMINESCENCE OF LED DEVICES BASED ON n-ZnO NANORODS GROWN BY VARIOUS METHODS AND p-GaN FILMS

B. I. Turko{1,*} , A. S. Nikolenko{2} , B. S. Sadovyi{3} , L. R. Toporovska{1} , M. S. Rudko{1} , V. B. Kapustianyk{1} , V. V. Strelchuk{2} , R. Y. Serkiz{1} , Y. O. Kulyk{1} 

1Ivan Franko National University of Lviv,
50, Drahomanov St., Lviv, 79005, Ukraine
2V. E. Lashkaryov Institute of Semiconductor Physics NAS of Ukraine
41, Nauky Ave., Kyiv, 03028, Ukraine
3Institute of High Pressure Physics PAS,
29/37, SokoĊ‚owska St., 01-142, Warsaw, Poland

Received 18 January 2020; in final form 17 September 2020; accepted 16 October 2020; published online 03 March 2021

Light emitting diodes (LEDs) structures based on $p$-GaN film/$n$-ZnO nanorods quasiarray heterojunction were fabricated. ZnO nanostructures were grown on the $p$-type GaN templates using two different methods. The turn-on voltages of ZnO/GaN heterojunctions based on ZnO nanorods grown using the gas-transport reaction and hydrothermal methods were equal to 3.2 V and 6.5 V, respectively. The diode-ideality factors were estimated to be of around 45 and 36 for the samples with ZnO nanorods grown using the method of the gas-transport reaction and the hydrothermal method, respectively. The large values of the ideality factors can be explained by a high density of trap states and quality of the contacts with the $p-n$ junctions. The electroluminescence (EL) spectra of LEDs with ZnO nanorods grown by the gas-transport reaction and hydrothermal methods were approximated by four and three Gaussians, respectively. On the basis of the $X$-ray diffraction (XRD), electrical and optical studies data, one can conclude that the emission peaks at 389-391, 410-412, 436-438 and 502 nm correspond to the near-band-edge (NBE) recombination in ZnO, interface carriers recombination in ZnO/GaN junction, the electrons transition from GaN conduction band to Mg$^{2+}$ doping level, and to the emission from the defect levels in ZnO, respectively. The LED based on ZnO nanorods synthesized using the hydrothermal method emitted a more pure ultraviolet (UV) light.

Key words: zinc oxide, gallium nitride, nanorods, heterojunction, electroluminescence

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