Scanning tunneling spectroscopy performed at T = 6 K is used to investigate the local density of states (LDOS) of electron systems in the bulk conduction band of InAs. In particular, the 3DES of the n-doped material and an adsorbate-induced 2DES located at the surface are investigated at B = 0 and 6 T. It is found that the 3DES at B = 0 T can be described by Bloch states weakly, interacting with the potential disorder, The 2DES at B = 0 T exhibits much stronger LDOS corrugations revealing the tendency of weak localization. In a magnetic field both systems show drift states, which are expected in 2D, but are surprising in 3D, where they point to a new electron phase consisting of droplets of quasi 2D-systems. (C) 2002 Elsevier Science B.V. All rights reserved.