The electronic density of states at clean surfaces of n-type In0.53Ga0.47As, grown by molecular beam epitaxy on lattice-matched (0 0 1)and (1 1 1)A-oriented InP substrates, was measured by low-temperature scanning tunneling spectroscopy under ultra-high vacuum. It was found that the surface Fermi level (FL) pinning strength dramatically depends on crystal orientation. The FL at the (0 0 1)-(2 x 4) surface is pinned near midgap, independently of the dopant concentration in the bulk. In contrast, the FL at the (1 1 1)A-(2 x 2) surface lies in the conduction band, close to the bulk FL, and increases with dopant concentration. (c) 2007 Elsevier B.V. All rights reserved.