Interdiffusion coefficients (
) were measured from 600 to 300 °C for HgTe‐CdTe diffusion couples. The influence of the binary composition, temperature, and Hg overpressure on
has been established. Significant differences have been found in the behavior of
in two temperature regions. A dual mechanism is proposed for diffusion at higher temperatures (T
≥450 °C), with a vacancy mechanism and an interstitial mechanism dominating at low and high x
value regions, respectively, and an interstitial mechanism predominating at lower temperatures. The proposed model is confirmed by electrical property, tracer diffusion, and theoretical studies, and provides a basis for predicting the interdiffusion behavior at even lower temperatures.