The effect of a p inversion layer along the free surface of a solid solution and the reverse current for metal/n-AlxGa1-x Sb surface barrier structures are analyzed. An algorithm is proposed for numerical solution of the system of equations which describes the "collection" of the current along the unbounded planar surface of a structure with a metallic contact of radius rc. During the calculations of the properties for surface barrier structures it was assumed that the positions of the Fermi level at the boundary with the metal and at the free n-Alx Ga1-x Sb surface are about the same. Calculations of the near-surface component of the reverse current Is for the structures with this assumption exceed the bulk component Ib by more than an order of magnitude. The dependences of Is and Ib and the effective radius of the collection region of the current on the composition of the solid solution are found. We compared the calculated current-voltage characteristics with the experimental ones for Pd/Al0.1, Ga0.9Sb structures. © 1999 Kluwer Academic/Plenum Publishers.