Optimum growth and properties of ZnS/GaAs(1 0 0) epilayers by hot-wall epitaxy

High quality ZnS epilayers were grown on GaAs (1 0 0) substrates by hot-wall epitaxy. From the lattice parameter and its dependence on the substrate temperature, it is found that there remains tensile strain in ZnS epilayers. The thickness dependence of the full-width at half-maximum of the double crystal rocking curves shows that the quality of the epilayers is good and gets better for thicker films. The very strong and very sharp exciton peaks near the band-edge with hardly observable deep level emissions indicate the high quality of the epilayers. The free exciton peak was observed up to room temperature and shifts to lower energy with increasing measurement temperature, which is due to the thermal tensile strain. From the temperature dependence of the free exciton energy, the room temperature energy gap was found to be 3.729 eV. (C) 1998 Elsevier Science B.V. All rights reserved.