Interface Shape under the Insulating Baffle in Vertical Bridgman Systems

Abstract

In the vertical Bridgman (VB) configuration, the shape of the solid–liquid (s/l) interface controls the yield and quality of single crystals. The two key effects for growing CdTe in VB configuration with the baffle is are considered: i) the thermal conductivity of the baffle and 2) baffle/crystal rotation. The baffle has a dominating effect on heat transfer to the s/l interface. The low thermal conductivity baffle (λ = 0.3 W m‐K−1) shields the s/l interface from the hot zones of the furnace above the baffle, so that the furnace temperature has to be increased, thus enforcing convex interface. The insulating baffle is expected to be particularly useful for growth of low conductivity crystals such as CdTe or CZT because heat conduction through the crystal is slow. The flow driven by the rotating crystal (i.e., ampoule) makes the interface less convex. By rotating the crystal relative to the baffle, the undesirable, unsteady natural convection can be made negligible compared to forced convection, thus providing steady laminar flow at the s/l interface.