In order to gain information on the micron-scale homogeneity of the InAs growth as a function of applied potential, Raman maps are shown in Figure for samples grown at a few potentials. The colour of each pixel represents the sum of the CCD counts under the TO and LO peaks (from 180 to 260 cm -1 ), indicated by the grey shade in Figure . At low laser intensities (top row) it is worth noting that every pixel in all maps exhibit the characteristic first-order InAs Raman peaks. Therefore, we conclude that InAs is grown all over the surface for all applied potentials within the diffraction limited resolution of the Raman map (i.e., ~ 240 nm). Despite small inhomogeneities in intensity, a quantitative assessment on the InAs thickness is not straightforward since (i) the Raman peak intensities also depend on the crystal orientation and (ii) the probing depth with 532 nm laser is limited to < 20 nm.