Single crystals of ZnSe, phosphorus-doped ZnSe and phosphorus with Gallium-doped ZnSe have been grown by physical vapour transport technique. The thermal properties like thermal diffusivity, effusivity and conductivity are studied using photoacoustic spectroscopy and differential scanning calorimetry, for the use of substrate. Their optical properties are also studied using Raman. photoluminescence and photocurrent for the study of the site symmetry of the phosphorus. Our measurements reveal the possibility of phosphorus going to deep level thus reducing to C-3v level. (C) 2002 Published by Elsevier Science B.V.