Metal-organic chemical vapour deposition (MOCVD) of compound semiconductors. Part 1.—Optimisation of reactor design for the preparation of ZnSe

Optimisation of the reactor design for the preparation of ZnSe by metal-organic chemical vapour deposition (MOCVD) at atmospheric pressure has been achieved using TiO2‘smoke’ experiments.Formal expressions derived from gas flow dynamics adequately describe the experimental situation in the laminar flow regime and the ‘stagnant layer’ observed above the hot graphite substrate holder (susceptor) can be treated in terms of boundary layer theory. The required dependences of the stagnant layer thickness (δ) on distance along the substrate holder (x), gas velocity (U∞) and temperature (T) are experimentally observed.Growth of ZnSe from dimethylzinc and H2Se on silica and GaAs(100) substrates has been achieved in this horizontal reactor at atmospheric pressure in a hydrogen flow. The growth rate (G) has been studied as a function of distance along (x) and across (z) the susceptor and as a function of temperature: G is independent of temperature between 555 and 645 K and is controlled by the diffusion of reactants across the stagnant layer.