Ball-and-stick model of the unreconstructed surface. The large balls with grey and black colors represent the topmost Ga and As atoms, respectively. The surface unit cell is defined by the vectors and . The inset shows a schematic figure of a (631) wafer with some crystallographic directions indicated.
(a) AFM image of a (631) surface obtained after the oxide desorption process. Insets (i) and (ii) show RHEED patterns of the surface taken after the oxide desorption process along the and directions, respectively. (b) AFM image of the surface of a thick GaAs layer; the surface presents a high density of hillocks.
(a) Arrhenius plots of the hillock length and width as a function of the inverse of the growth temperature. (b) Variation of the hillock height as a function of the growth temperature. The inset shows the hillock density as a function of growth temperature; the continuous line shows a fitting to an exponentially decaying function.
Hillock length, width, and height as a function of the ratio with a constant growth temperature of . The inset in (b) shows an AFM image of the surface of the sample grown at .
PR spectra from the set of samples grown at different temperatures. The spectrum RS is from a desorbed GaAs(631) substrate. The solid lines show the fittings to the Aspnes third-derivative functional form. The arrows indicate the energy transitions and found by the fits. The inset shows the variation of as a function of the hillock density.
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