Diffusion of phosphorus in CdTe

The diffusion of phosphorus in CdTe was measured as a function of anneal time and temperature in the temperature range 600-900°C. The diffusion anneals were carried out in evacuated silica capsules mainly with traces of radioactive phosphorus in the capsule along with sufficient cadmium metal to maintain a saturated vapor pressure over the CdTe slice throughout each anneal. The concentration profiles were measured using a radiotracer sectioning technique. Diffusion anneals were carried out also using other conditions, including some with excess tellurium in the capsule in place of the cadmium. The diffusion profiles were single component. The standard erfc function gave satisfactory fits to the profiles which were Fickian in nature except for short anneal times at intermediate temperatures. When the diffusivity was plotted on an Arrhenius graph, a straight line was obtained giving an activation energy of 2.0 eV. The surface concentration at each temperature was independent of time and varied in value between 1.5×10¹⁶ cm^-3 at 600°C to 1×10¹⁸ cm^-3 at 900°C. When the results were plotted on an Arrhenius graph, the results gave a straight line with an activation energy of 1.3 eV.