Self-Directed Growth of AlGaAs Core−Shell Nanowires for Visible Light Applications

Abstract

Be-doped Al 0.37 Ga 0.63 As nanowires (NWs) were grown in a molecular beam epitaxy system on GaAs (111)B substrates. Visible light emission was observed at room temperature in a confocal microscope and by micro-photoluminescence (μPL) measurements. μPL polarization measurements at 10 K, and diffusion measurements of NWs in solution, indicated emission from single NWs. Energy dispersive X-ray spectroscopy indicated a core-shell structure and Al composition gradient along the NW axis, producing a potential minimum for carrier confinement. The core-shell structure formed during growth as a consequence of the different Al and Ga adatom diffusion lengths.

Heterostructured III-V Nanowires with Mixed Crystal Phases Grown by Au-Assisted Molecular Beam Epitaxy

“…It is important to note that no PL emission was observed from bare GaAs core NWs at RT. As has already been reported by several authors (Titova et al, 2006;Chen et al, 2007), the shell in the GaAs/AlGaAs core-shell NW helps to increase the radiative recombination efficiency by approximately two orders of magnitude through the suppression of nonradiative surface recombination at the GaAs surface. As can be seen in Fig. 14, PL emissions from both GaAs and AlGaAs are observed at low temperature.…”

“…This was theoretically explained by Dubrovskii et al, 2005, attributing the diameter dependence of the NW growth to the diffusion of group III adatoms from the substrate surface to the Au particle. The demonstrations of the growth of homogeneous binary compound NWs, including GaAs, InP, InAs and GaP by MBE (Cornet et al, 2007;Harmand et al, 2005; were followed by the growth of heterostructures involving ternary compounds such as AlGaAs, InGaAs, GaAsSb, InAsP and GaAsP (Chen et al, 2006;Chen et al, 2007;Cornet & LaPierre, 2007, Dheeraj et al, 2008a. However, the progress in the MBE growth of ternary compound NWs involving different group III elements, such as AlGaAs and InGaAs, has been inhibited due to difficulties in obtaining uniform composition along the length of the NW.…”

“…The occurrence of several PL peaks is believed to be due to some local composition variations (10-15%) in this AlGaAs region. It has already been reported that for the axial VLS growth of AlGaAs on top of GaAs, a selfformed AlGaAs core-shell structure is formed with a radial variation in the Al composition (Chen et al, 2007). The existence of AlGaAs related PL peaks from the GaAs/AlGaAs coreshell NWs suggests that there is room for improvement of the growth, especially by reducing the axial growth of AlGaAs…”

Structural and optical analysis of GaAsP/GaP core-shell nanowires

“…Of particular interest is the use of core-shell NW architectures, composed of ternary III-V compound semiconductor alloys, which provide further freedom to tune the material bandgap including the optical frequency range. [2][3][4][5] Encapsulation of core NW segments by higher bandgap shell layers provides passivation of surface states, where nonradiative recombination transitions are prevalent, as well as the confinement of charge carriers within the core segment.…”

FIB Method of Sectioning of III-V Core-Multi-Shell Nanowires for Analysis of Core/Sell Interfaces by High Resolution TEM

“…The pseudo-one-dimensionality of NWs offers a unique opportunity to control sizedependent and structure-dependent material properties for novel device functionalities. The use of core-shell NW architectures, composed of ternary III-V compound semiconductor alloys is of particular interest and provides further freedom to tune the material bandgap [2]. Nanowires grown in the core-shell geometry attract a great interest because of possible applications as building blocks of different devices, such as solar cells [3], high electron mobility transistors [4], light emitting diodes [5], and lasers [6].…”