Control of III-V epitaxy in a metalorganic chemical vapor deposition process: Impact of source flow control on composition and thickness

A procedure for developing a real-time automated control system for improving epitaxial growth of semiconductors is presented and applied to GaInAs growth by metalorganic chemical vapor deposition. Vapor concentration variations of the gallium source are identified as a primary disturbance. An analog control system that regulates the supply of gallium is designed and implemented, Key issues in the controller synthesis are outlined. The controller performance is investigated by growing GaInAs/InP superlattices. Results of growths performed under normal operating conditions and also under large perturbations are presented. These results include X-ray diffraction from the samples as well as real-time data from the concentration monitor and the flow measurement. High quality superlattices that display up to eight orders of satellite peaks are obtained under closed loop control, demonstrating improved layer-to-layer reproducibility of thickness and composition.