Low-temperature scanning tunneling microscopy of subsurface shallow dopants: depth dependence of the corrugation for the GaAs(110) surface

We investigated the corrugations induced by subsurface donor and acceptor atoms in low-temperature STM images of the (110) surface of doped GaAs single crystals. When the impurities are screened by Friedel charge-density oscillations, the height distribution for Si and Te donors exhibits an oscillatory behavior with four maxima being observable. We argue that these maxima do not correspond to dopant atoms in four different subsurface layers. The maxima rather correspond to four periods in the oscillatory dependence of the corrugation height on the depth of the impurity, which has been predicted by Kobayashi [Phys. Rev. B 54, 17 029 (1996)]. When the charged impurities are not screened, the height of the hillocks induced by donors, and the depth of the depressions induced by acceptors reveal an exponentially decaying distribution.