Ballistic-electron-emission microscopy (BEEM) has been used to study the Schottky-barrier formation at the Au/n-ZnSe interface. Spectroscopy measurements indicate that the Schottky-barrier heights present unusually large variations and range from 1.53 to 2.15 eV. The lowest values are in good agreement with the barrier heights obtained from macroscopic current-voltage (I-V) measurements. The possible reasons for the existence of large Schottky-barrier variations are presented and discussed in this paper. These include the effect of variations of the work function and the behavior of the contact as a metal-insulator- semiconductor structure due to microclusters of different phases at the interface. Contrasts in the BEEM image are also found to follow the gold grain boundaries and are assumed to depend both on the grain orientation and interface quality. © 1995 The American Physical Society.