The far infrared reflectance technique has been used to characterize ZnTe and CdTe films grown using Metal Organic Chemical Vapor Deposition (MOCVD) on GaAs substrates. Carrier concentrations, derived from the reflectance measurements, decreased with increasing ZnTe film thickness as a result of the large lattice mismatch between ZnTe and GaAs. This mismatch produces a high strain, high dislocation region near the interface. The uniformity of CdTe films grown on GaAs substrates in two different types of reactors are compared. The thickness and carrier concentration is found to be far more uniform for films grown in a vertical flow, rotating susceptor reactor than for films grown in a conventional linear flow reactor.