New way to nanopattern GaAs surface for subcritical formation of InAs quantum dots

This paper proposes a new approach to nanoscale patterning of GaAs substrates that allows formation of subcritical (below the Stranski-Krastanov critical thickness) low-density quantum dots. We demonstrate that the removal of the GaAs native oxide under molecular arsenic flux stimulates the formation of nanosized holes on the substrate surface. Geometric characteristics of these holes (diameter, depth and shape) can be controlled by the variation of the oxide thickness and the parameters of the oxide removal procedure. Importantly, the surface density of resulting holes shows a weak dependence on the listed parameters and remains around 1 x 109 cm-2. We show that the arsenic flux influences the processes of hole formation during the GaAs native oxide removal mainly by the modulation of the substrate thermal decomposition. We experimentally demonstrate the possibility of using GaAs substrates patterned in this way as templates for obtaining subcritical InAs quantum dot arrays with low density. We observe complete suppression of the wetting layer formation on such templates and a pronounced red shift of the emission wavelength of quantum dots grown on them (up to 1080 nm). Our results suggest that further optimization of the proposed approaches will make it possible to form low-density quantum dots emitting in the O- and C-bands.