Control of a III-V MOCVD process using ultraviolet absorption and ultrasonic concentration monitoring

Metalorganic chemical vapor deposition (MOCVD) is a key technology for the growth of compound semiconductors. This process has traditionally lacked real-time growth monitoring and control, which limits the precise reproducibility needed for high performance devices. Two complementary control approaches for the MOCVD process are investigated experimentally. The first one is a feedforward disturbance rejection strategy using ultrasonic concentration measurements to reject source gas bubbler disturbances. The second one is a feedback system using an ultraviolet absorption sensor for real-time monitoring of reaction chamber gas concentrations. Post-growth X-ray diffraction and photoluminescence of InP/GaInAs superlattice test devices are used to evaluate the control system performance.