GaSb and InSb Quantum Nanostructures: Morphologies and Optical Properties

Abstract

GaSb/GaAs and InSb/GaAs material systems can create type-II quantum nanostructures which provide interesting electronic and optical properties such as having long carrier life time, low carriers-recombination rate, and emitting/absorbing low photon energy. These characteristics of type-II nanostructures can be applied for infrared or gas detection devices, for memory devices and even for novel intermediate band solar cells. In contrast, lattice mismatches of GaSb/GaAs and InSb/GaAs material system are 7.8% and 14.6%, respectively, which need some specific molecular beam epitaxial (MBE) growth conditions for quantum nanostructure formation via Stranski–Krastanov growth mode.

In this paper, the growth of self-assembled GaSb and InSb quantum nanostructures on (001) GaAs substrate by using MBE was reported. The surface morphology of these two quantum nanostructures and their optical properties were characterized by atomic force microscopy and photoluminescence (PL). The experimental results were compared between these two quantum nanostructures. Due to the lattice mismatch in each material system and the difference in sticking coefficient of Ga- and In-atoms during epitaxial growth, we obtain GaSb/GaAs quantum dots (QDs) with a density ∼10¹⁰ dots/cm² and InSb/GaAs QDs with a density of ∼10⁸ dots/cm². The facet analysis of individual quantum nanostructure in each material system reveals that GaSb/GaAs QD has a dome-like shape with nearly isotropic property while InSb QDs form a rectangular-like shape with elongation along [110]-direction showing a strong anisotropic property.

Low temperature PL spectra from capped GaSb and InSb quantum nanostructures show the energy peaks at 1.08-1.11 and 1.16-1.17 eV, respectively. The variations of PL peaks as a function of both temperature and excitation power are investigated. PL peak shows clear blue shift when excitation power is increased. This work manifests a possibility to use both GaSb and InSb quantum nanostructures for nanoelectronic and nanophotonic applications.