Synthesis and characterization of silicon-doped gallium oxide nanowires for optoelectronic UV applications

Abstract

Silicon-doped gallium oxide nanowires have been synthesized by thermal methods using either a mixture of gallium oxide and silicon powders or metallic gallium with silicon powder as precursor materials. The growth mechanism has been found to be a vapour-liquid-solid (VLS) or vapour-solid (VS) process, respectively, depending on the precursor used. In the former case, silicon oxide droplets at the end of the nanowires have been observed. Their possible role during the growth of the nanostructures is discussed. Structural and morphological characterization of the doped nanowires has been performed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The results show a high crystalline quality and a uniform distribution of silicon along the nanowires. Room temperature cathodoluminescence (CL) in the SEM shows that slight variations in the composed UV-blue emission band appear due to the influence of Si impurities in the oxygen vacancy defect structure.

Donor–Acceptor Control in Grown‐in‐Glass Gallium Oxide Nanocrystals by Crystallization‐driven Heterovalent Doping

“…We obtain Gaussian components centered at 2.47, 2.89, and 3.75 eV—with bandwidth σ =0.24, 0.33, and 0.33 eV, respectively. The analysis of the three components is consistent with the occurrence of previously identified mechanisms of UV, blue, and green emission in Ga oxide systems, respectively ascribed to decay of self‐trapped excitation, DAP recombination, and radiative transition at V Ga sites . Even the spectral parameters are consistent with previous analyses, provided that one takes into account the change of spectral distributions from PL intensity spectra to emitted power spectra, which we calculated as PL signal intensity divided by the squared wavelength .…”

“…A spectral contribution comes from radiative recombination at donor and acceptor pairs (DAPs), with neutral oxygen vacancies V O acting as donors, and complexes of oxygen and Ga vacancies [ V O , V Ga ] X behaving as acceptors . Two additional components occur in the green and UV regions at 550 nm and just below 400 nm, ascribed to radiative transition at V Ga sites and, respectively, from decay of self‐trapped excitation probably mediated by sub‐band gap levels as V O sites . Therefore, V O and V Ga sites turn out to govern the spectral and kinetic features of light emission in Ga oxide nanophases.…”

“…[35] Twoa dditional components occur in the green and UV regionsa t5 50 nm and just below 400 nm, ascribed to radiativet ransition at V Ga sites and, respectively, from decay of self-trapped excitation probablym ediated by sub-bandg ap levels as V O sites. [35][36][37][38][39] Therefore, V O and V Ga sites turn out to govern the spectrala nd kinetic features of light emission in Ga oxide nanophases.…”

Diffusion-driven and size-dependent phase changes of gallium oxide nanocrystals in a glassy host

“…3,47 Additional distinct spectral contributions in the green and UV regions are sometimes observed and can be respectively ascribed to electron-hole recombination between oxygen and gallium vacancies and to exciton-like decay mediated by sub-band gap levels. [51][52][53][54] Looking at Fig. 10, we can notice two important features.…”

Light-emitting Ga-oxide nanocrystals in glass: a new paradigm for low-cost and robust UV-to-visible solar-blind converters and UV emitters

“…The UV emission arises from exciton-like decay mediated by sub-band gap levels, mainly observed in doped materials but also in pure single crystals. 7,[10][11][12][13][14] Since UV-excited light emission is accompanied by good transmittance and no excitation channel in the whole visible and near-UV spectrum, Ga 2 O 3 -based materials can be considered particularly suitable systems, in principle, for the fabrication of simple and robust fully inorganic UV-to-visible converters. Such optical components could be coupled to silicon-based commercial detectors for the imaging of UV events, without any signal intensier, which makes the visible view problematic under daylight conditions for saturation, unless some complex double detection system is employed.…”