The Co/n-GaAs(Te) Schottky barrier diodes have been annealed at temperatures from 100 to 300 degrees C for 5 min and from 350 to 800 degrees C for 1 min in N-2 atmosphere. Some expressions have been obtained to interpret the relation between the experiment barrier height Phi(b,o) and equilibrium interface charge density Q(ss)(0) depending on annealing temperature. The Phi(b,o) value has increased and Q(ss)(0) is decreased with increasing annealing temperature up to 550 degrees C. This increase in the barrier height has been attributed to the value of positive Q(ss)(0), which is responsible for the Fermi level pinning. The relation between the Phi(b,o), and Q(ss)(0) depending on annealing temperature is in very good agreement with that of the interface state density distribution especially in the mid-gap. (C) 2000 Elsevier Science Ltd. All rights reserved.