Computer controlled deposition of cmt heterostructures by Movpe

A versatile reactor has been developed for the epitaxial deposition of multilayer CMT heterostructures, using the metal alkyls dimethyl cadmium and diethyl tellurium. The IMP (Interdiffused Multilayer Process) deposition technique is employed for achieving good compositional uniformity. Particular features of the reactor include a resistance heated susceptor and modified cadmium alkyl injection technique, this minimises the adverse effects of dead space in the mercury source region of the reactor tube. Gas flow switching is by computer controlled operation of solenoid valves, this is necessary for the satisfactory operation of the IMP technique, it also allows the programmed growth of a sequence of layers with different alloy compositions. Provision is made for the impurity doping of layers during growth, using gaseous or liquid sources. The capabilities of the growth system will be discussed in relation to the physical and chemical characteristics of doped and undoped epitaxial layer structures. Assessment techniques that have been used include SIMS, X-ray fluorescence, infra-red transmission measurements and scanning electron microscopy.