Abstract
We developed photoassisted MBE of ZnSe on GaAs (100) substrates using a He-Cd laser (441.6nm). The epilayer thicknesses were reduced by the irradiation during growth and also after growth. Photodesorption rate constant of adatoms were obtained and it was clarified that these photodesorption were photo-enhanced thermal desorption. The desorption was enhanced totally under the coexistence of the photogenerated electrons and holes at the epilayer surface. Adsorption and desorption processes of Zn and Se adatoms on the ZnSe (100) surface were also investigated by RHEED. Chopped irradiation was used during growth and it was revealed that the effects persisted about 5 ms after the light was turned off.
Reduction in the density of hillocks, extension of the critical thickness, increase in the intensities of free-exciton emissions and lowering of the epitaxial temperature (150°C) were realized by photoassisted MBE. These improvements due to the irradiation can be explained by the migration enhancement of surface adatoms by the irradiation. Light irradiation effects on doping of impurities were investigated. A model of selective transfer of photogenerated carriers is proposed and the behavior of surface adatoms is discussed.
