The synthesis of single-phase gamma -In2Se2.5Te0.5 alloy thin films with low substitution of selenium by tellurium was carried out by a direct method from In and (Se1-xTex) thermal evaporation and a subsequent heat treatment. A correlation between the film properties and alloy composition was observed. These gamma -In2Se2.5Te0.5 films changed from p-type conduction to n-type by the addition of Te, and showed a high optical absorption coefficient (alpha > 10(4) cm(-1)) and an energy gap of about 1.45 eV, narrower that of gamma -In2Se3 thin films, An improvement of the electronic transport properties, i.e., the carrier concentration and mobility, was achieved as proved by electrical conductivity and Hall measurements. (C) 2000 Elsevier Science Ltd. All rights reserved.