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Gas-source molecular beam epitaxy and a formulation for the growth control of a class of quaternary materials

Research in the control of gas-source molecular beam epitaxy (GSMBE) suggests that previous results for the growth of ternary III-V alloys via an alternative process, metal organic chemical vapor deposition (MOCVD), extend nicely to the problem of growing quaternary compounds of the form A/sub x/B/sub 1-x/C/sub y/D/sub 1-y/ by GSMBE. In fact, the growth control problem for ternary compounds via MOCVD turns out to be embedded in the growth control problem for quaternary compounds via GSMBE. This is striking since the dynamics of MOCVD, which are linear, differ considerably from those of GSMBE, which are strongly nonlinear. Nevertheless, structure in the models can be exploited via an appropriate change of coordinates to facilitate controller design using linear design methodologies. Resulting controllers are shown to be robust with respect to parametric model uncertainty. The experimental setup of facilities under development is also discussed in light of future applications of this work.