Jiangong Cui

Fabrication and optical properties of multishell InAs quantum dots on GaAs nanowires

Hybrid nanostructures combining nanowires with quantum dots promote the development of nanoelectronic and nanophotonic devices with integrated functionalities. In this work, we present a complex nanostructure with multishell quantum dots grown on nanowires. 1–4 shells of Stranski-Krastanov InAs quantum dots are grown on the sidewalls of GaAs nanowires by metal organic chemical vapor deposition. Different dot shells are separated by 8 nm GaAs spacer shells. With increasing the number of shells, the quantum dots become sparser and tend to align in one array, which is caused by the shrinkage of facets on which dots prefer to grow as well as the strain fields produced by the lower set of dots which influences the migration of In adatoms. The size of quantum dots increases with the increase of shell number due to enhanced strain fields coupling. The spectra of multishell dots exhibit multiwavelength emission, and each peak corresponds to a dot shell. This hybrid structure may serve as a promising element in nanowire intermediate band solar cells, infrared nanolasers, and photodetectors.

Controllable growth and optical properties of InP and InP/InAs nanostructures on the sidewalls of GaAs nanowires

The growth and optical properties of InP and InP/InAs nanostructures on GaAs nanowires are investigated. InP quantum well and quantum dots (QDs) are formed on the sidewalls of GaAs nanowires successively with increasing the deposition time of InP. The GaAs/InP nanowire heterostructure exhibits a type-II band alignment. The wavelength of the InP quantum well is in the range of 857–892 nm at 77 K, which means that the quantum well is nearly fully strained. The InP quantum dot, which has a bow-shaped cross section, exhibits dislocation-free pure zinc blende structure. Stranski-Krastanow InAs quantum dots are subsequently formed on the GaAs/InP nanowire core-shell structure. The InAs quantum dots are distributed over the middle part of the nanowire, indicating that the In atoms contributing to the quantum dots mainly come from the vapor rather than the substrate. The longest emission wavelength obtained from the InAs QDs is 1039 nm at 77 K. The linewidth is as narrow as 46.3 meV, which is much narrower than those on planar InP substrates and wurtzite InP nanowires, suggesting high-crystal-quality, phase-purity, and size-uniformity of quantum dots.

Growth and characterization of InAs quantum dots on InP nanowires with zinc blende structure

InAs quantum dots (QDs) are grown epitaxially on the {112} side facets of InP nanowires (NWs) by metal organic chemical vapor deposition. The QDs typically have a large size and consist of some specific facets. The QDs exhibit mainly zinc blende structure with stacking faults, which is consistent with the adjacent NW. No QDs are observed on the wurtzite (WZ) part of NW, which is attributed to a lower surface energy of WZ facet. The random distribution of the QDs indicates that the In adatoms may mainly come from the vapor rather than the substrate.

Realization of Stranski–Krastanow InAs quantum dots on nanowire-based InGaAs nanoshells

We investigate the formation and optical properties of InAs quantum dots on an InGaAs nanosubstrate. We find that Stranski–Krastanow InAs quantum dots are hardly formed on Au-catalyzed InGaAs nanowires due to the phase separation as well as stacking faults. High-quality Stranski–Krastanow InAs quantum dots are realized on a pure zinc blende InGaAs shell radially grown on a GaAs nanowire core. The quantum dots have a large size and regular shape, residing on a wetting layer of several nanometers. For optical characterization, we fabricate a “dot-in-well” structure by capping the quantum dots with InGaAs/GaAs double layers. Photoluminescence from the quantum dots is observed at 77 K, with a peak wavelength of 954 nm, which is distinctly redshifted compared with that of InAs quantum dots directly grown on GaAs nanowires. This work shows the potential of growing Stranski–Krastanow QDs on more types of NWs and obtaining longer wavelengths for wider applications.

Morphological and temperature-dependent optical properties of InAs quantum dots on GaAs nanowires with different InAs coverage

We report a study on the morphological and temperature-dependent optical properties of InAs quantum dots on GaAs nanowires with different InAs coverage. We find that the size, density, and distribution of quantum dots strongly depend on the InAs coverage. At higher coverage, the quantum dots exhibit a longer peak wavelength and broader linewidth at low temperature, suggesting a larger size and increased size fluctuations. Particularly, a great difference in the linewidth dependence on temperature for different InAs coverage is observed, corresponding to a different result of competition between electron-phonon scattering and thermal penetration of carriers between neighboring quantum dots.

Effect of dangling bonds on the doped GaAs nanowires

We have investigated the effect of surface dangling bonds on the doped GaAs nanowires by the first-principle density functional calculation. Our results show that the surface dangling bonds prefer to deactivate the p-type dopants.