Reverse current-voltage characteristics of Al-GaP Schottky diodes are studied in the temperature range from 213 to 373 K. The results are explained on the basis of phonon-assisted electron tunneling from interface states to the semiconductor conduction band. At low bias and higher temperatures the Frenkel emission mechanism is taken into account. Electric field strength and the density of generating centres in the junction is estimated from the fit of experimental results with theory. The temperature and field dependence of the leakage current in thin film transistors extracted from Ref. [Solid-State Electron 38 (12) (1995) 2075] is also explained on the basis of our model. (C) 2002 Published by Elsevier Science Ltd.