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While on GaAs(001) three-dimensional (3D) growth of InAs quantum-dots (QD) is observed on GaAs surfaces, such as the (110), the InAs deposition typically results in a two-dimensional (2D) growth and the misfit relaxes plastically. {110} facets often form the sidewalls in self-assembled GaAs nanowires. And the growth of 3D nanostructures like quantum dots on these sidewalls is of high interest for light emitting devices [1]. Recent investigations show that the presence of surface Bismuth (Bi) induces 3D growth on GaAs(110) by modifying the surface energy [2]. Furthermore, Bi exposure on already grown 2D InAs layers causes a morphological phase transition, resulting in a rapid re-organization of the 2D layer into 3D nanostructures. These so-called 3D islands have optical properties of quantum dots and open the possibility to generate linearly polarized single photons [1].
We investigate these 3D InAs islands grown on GaAs(110) substrate using cross-sectional scanning tunnelling microscopy (XSTM). For this purpose, we cleaved the sample containing capped InAs/GaAs(110) layers with four different growth conditions and Bi contents in ultra-high vacuum perpendicular to the [110] growth direction. Atomically resolved XSTM images allow for the characterization of the geometric structures in terms of size, density, and atomic composition depending on the presence of Bi. Furthermore, we carry out stoichiometric analysis of the chemical composition by analyzing the variation of local lattice parameter [3]. Thus, we are able to contribute to better understanding of the growth mechanisms of InAs/GaAs(110) with Bi in order to improve the properties for device applications.
References:
[1] P. Corfdir et al. Phys. Rev. B 96, 045435 (2017)
[2] R. B. Lewis et al. Nano Lett,17,4255-4260 (2017)
[3] A. Lenz et al. J. Vac. Sci. Technol. B 29, 04D104 (2011)
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