A HIGH-SPEED, ROTATING-DISC METALORGANIC CHEMICAL-VAPOR-DEPOSITION SYSTEM FOR THE GROWTH OF (HG, CD)TE AND RELATED ALLOYS

A high-speed, rotating-disc metalorganic chemical vapor deposition (MO CVD) system has been developed for the growth of (Hg,Cd)Te and related alloys. Traditional MOCVD reactors do not control density gradient dr iven convection currents generated by nonuniform gas heating. The rota ting disc interacts dynamically with gas flow in a manner that can be used to control the effects of gas thermal expansion. When the sample pedestal is rotated at high speed, viscous drag on the rotating disc s urface creates a subductive gas flow at the center of the reactor. The opposing effect of convective buoyancy created by non-uniform gas hea ting can be neutralized, establishing stable forced laminar flow throu gh proper choice of disc rotation rate and other operating conditions. An important novel aspect of this system design individually separate s introduction of the tellurium and cadmium precursors from the combin ed mercury/bulk hydrogen flow in a manner that results in independent control of the cadmium and tellurium concentrations across the entire area of the deposition plane. As a result, uniform chemical access to the growth surface is achieved and highly uniform alloy films are obta ined. These are the first reported results using the high-speed, rotat ing-disc system for growth of (Hg,Cd)Te. Basic system design concepts and technical details of both system construction and operation are re ported. The system has been used to successfully demonstrate reproduci ble growth of high quality (Hg,Cd)Te on multiple substrates. Operation al parameters and experimental results are reported, including slice-t o-slice and run-to-run uniformity data. CdTe, ZnTe and (Cd,Zn)Te buffe r layers grown in-situ using this single MOCVD system have previously been reported; initial results for (Hg,Zn)Te, CdSe and ZnSe film growt h are also reported; future reports will include other wide band gap ( Cd,Zn)(Te,Se) alloys.