Factors influencing low-temperature photo-assisted OMVPE growth of ZnSe

Abstract

The influence of temperature and ultraviolet (UV) light intensity on the optical characteristics of low-temperature, photo-assisted OMVPE growth of ZnSe on GaAs substrates has been studied. The epitaxial ZnSe was grown using the sources DMSe, DMZn and DMCd, with growth temperature varied from 360 to 400°C. We found that the UV intensity strongly influenced the optical quality of the epitaxial ZnSe layer. More intense near band-edge emission (NBE) is observed when the temperature is reduced from 400 to 360°C. The deep-level emissions (DLE) show a threshold-like dependence on UV light intensity for a given temperature. Beyond the threshold value of UV intensity the surface morphology improves and deep-level emissions are suppressed. Also, the UV threshold decreases with increasing growth temperature. The resulting ratio of near band-edge to deep-level emission intensity suggests the use of lower growth temperature and high UV intensity for blue-green light-emitting devices. The effect of cadmium doping on the optical properties of ZnSe was also investigated. Cadmium doping is found to improve the NBE/DLE photoluminescence intensity ratio, and this improvement is more pronounced at higher growth temperature.