Implicit linear control law of a close-spaced vapor transport process

Concerns the control of dopant incorporation in semiconductor materials grown from vapor. The technique considered involves deposition by the combined use of free evaporation and close-spaced vapor transport (CSVT). This technique has been used to grow indium-doped CdTe films with good electrical properties; the main goal for the study was to use the indium source temperature as a pertinent doping control parameter. In this paper we use a linear control scheme for the temperature, which has not to tune again when changing set point and the temperature error goes asymptotically to zero. This controller is composed of two linear control laws; the inner controller is an implicit control law which transforms the system in a linear time invariant system without disturbances, and the outer controller is a classical PI control law which makes the error tend to zero.