Emergence of Localized States in Narrow GaAs/AlGaAs Nanowire Quantum Well Tubes

Abstract

We use low-temperature photoluminescence, photoluminescence excitation, and photoluminescence imaging spectroscopy to explore the optical and electronic properties of GaAs/AlGaAs quantum well tube (QWT) heterostructured nanowires (NWs). We find that GaAs QWTs with widths >5 nm have electronic states which are delocalized and continuous along the length of the NW. As the NW QWT width decreases from 5 to 1.5 nm, only a single electron state is bound to the well, and no optical excitations to a confined excited state are present. Simultaneously, narrow emission lines (fwhm < 600 μeV) appear which are localized to single spatial points along the length of the NW. We find that these quantum-dot-like states broaden at higher temperatures and quench at temperatures above 80 K. The lifetimes of these localized states are observed to vary from dot to dot from 160 to 400 ps. The presence of delocalized states and then localized states as the QWTs become more confined suggests both opportunities and challenges for possible incorporation into quantum-confined device structures.

Conductance oscillations of core-shell nanowires in transversal magnetic fields

“…This provides a possibility to achieve thin tubular shells surrounding a core nanowire or other shells. One of the advantages of these systems is a possibility to establish band alignment through the thicknesses of the components [2][3][4] and thus grow structures in which electrons are confined only in narrow shell areas [5,6]. Moreover, the core part may be etched such that separated nanotubes are formed [7,8].…”

Magnetophotoluminescence in GaAs/AlAs core-multishell nanowires: A theoretical investigation

“…Long single-crystal defect-free cores [6,7], selective radial doping [8], and lateral overgrowth with high-quality interfaces [9] have been successfully realized. Most importantly, complex radial modulation doped heterostructures are now being engineered in coremultishell NWs [10][11][12][13]. More complex than their planar counterparts, radial heterostructures in these systems may host high-mobility electron/hole gases with an inhomogeneous localization in the section of the NW, which strongly depends on doping density and gate potentials [14][15][16].…”

“…Intraband optical spectroscopy is a key component in the investigation of properties of single semiconductor NWs and NW heterostructures [11][12][13][23][24][25][26]. In particular, photoluminescence (PL) has been successfully used in bare and core-multishell (CMS) NWs in order to analyze the dynamics of photoexcited electron-hole plasmas [23][24][25] and the quantum confinement effects [11][12][13].…”

Electron localization and optical absorption of polygonal quantum rings

“…Such nanowires are usually grown vertically and, due to the crystallographic structure, have polygonal cross sections, most commonly hexagonal [12][13][14], but triangular [6,8,9,15], square [16,17], and dodecagonal [18] cross sections are also feasible. Sharp edges along the wires induce unique carrier localization, which leads to formation of one-dimensional (1D) channels in corner or side areas [19][20][21][22][23][24][25].…”

“…It is also possible to etch the core part and achieve hollow nanowires [13,14], i.e., nanotubes of finite thickness. Multishell structures allow growth of narrow (up to 1.5 nm) tubes which are formed between two shell layers such that surface effects are reduced [19,24,25]. A polygonal nanoring may be considered as a short wire of this kind.…”