Observing visible-range photoluminescence in GaAs nanowires modified by laser irradiation

Abstract

We study structural and chemical transformations induced by focused laser beam in GaAs nanowires with axial zincblende/wurtzite (ZB/WZ) heterostucture. The experiments are performed using a combination of transmission electron microscopy, energy-dispersive X-ray spectroscopy, Raman scattering, and photoluminescence spectroscopy. For the both components of heterostructure, laser irradiation under atmospheric air is found to produce a double surface layer which is composed of crystalline arsenic and of amorphous GaO x . The latter compound is responsible for appearance of a peak at 1.76 eV in photoluminescence spectra of GaAs nanowires. Under increased laser power density, due to sample heating, evaporation of the surface crystalline arsenic and formation of β-Ga 2 O 3 nanocrystals proceed on surface of the zinc-blende part of nanowire. The formed nanocrystals reveal a photoluminescence band in visible range of 1.7-2.4 eV. At the same power density for wurtzite part of the nanowire, total amorphization with formation of β-Ga 2 O 3 nanocrystals occurs.Observed transformation of WZ-GaAs to β-Ga 2 O 3 nanocrystals presents an available way for creation of axial and radial heterostuctures ZB-GaAs/β-Ga 2 O 3 for optoelectronic and photonic applications.

Unified mechanism of the surface Fermi level pinning in III-As nanowires

“…These results clearly provide evidence that the surface excess arsenic in the crystalline or amorphous forms is the origin of the surface states responsible for surface nonradiative recombination and for the surface Fermi level pinning. These observations agree with the already known results observed on the photooxidation of GaAs nanowires [24,26].…”

“…After irradiation of the nanowire by a beam with the power density of 500 kW/cm 2 , the band-edge PL was not detected, which indicated that the PL intensity decreased by at least 3 orders of magnitude. At the same time, a weak PL appeared near 1.8 eV, which was apparently related to the formation of the GaO x layer [26]. The observed elimination of the band-edge PL intensity arose from the entire oxidation of the core / shell interface.…”

“…A photooxidation-induced decrease of the band-gap photoluminescence (PL) intensity for GaAs nanowires is observed [24]. We have recently shown that photooxidation leads to the formation of a double layer c-As/ GaO x at the GaAs nanowire surface and it is the c-As layer that contacts the crystal lattice of the nanowire [26].…”

Simulation Study on the Defect Generation, Accumulation Mechanism and Mechanical Response of GaAs Nanowires under Heavy-Ion Irradiation

“…In addition to these cases, structural transitions of amorphization or transition to another crystalline state usually occur in irradiated nanostructured materials. Amorphization and cubic-hexagonal transition phenomena [16,17] of Si NWs under irradiation conditions were found by Dai et al and Rodichkina et al, while Alekseev et al [18] also showed that radiation leads to amorphization in ZB/WZ heterostructure GaAs NWs, where the WZ structure transforms into β-Ga 2 O 3 crystals. Meanwhile, there is continuous progress in the study of the mechanical properties of irradiated GaAs NWs.…”

Control of Conductivity of InxGa1–xAs Nanowires by Applied Tension and Surface States

“…In all cases mentioned above, the surface Fermi remains at the same distance of 4.8 eV from the vacuum level . Such pinning behavior was assumed to be induced by a layer of As , atoms forming at the NW surfaces because of incomplete oxidation of the III–As materials in ambient atmosphere.…”