point plus capping layer such as the te rich cdte layer in connection with fig4 an alternative to the preferred embodiment method uses solid te on the substrate for gettering with the substrate temperature held between 300 u00b0 c and 449 u00b0 c the melting point of te the te may be evaporated onto the substrate and is roughly analogous to hg 1 x cd x te gettering but the te is near within 150 u00b0 c its melting point which implies a large vacancy concentration and effective gettering whereas the hg 1 x cd x te is about 400 u00b0 c below its melting point also the use of te avoids use of hg which is toxic as with the other embodiments after the annealing remove the surface gettering material together with the gettered impurities by polishing or diamond point turning further other films containing precipitated te could be used in place of the pure te film and still provide the gettering for example films such as cdte te cd te zn te znte te and so forth depending upon the substrate material fig5 shows an apparatus for use with a condensation preferred embodiment method of impurity gettering first load cdznte substrate 504 which typically is about 10 mm by 20 mm by 1 mm thick plus cd 508 of about 10 100 mg into ampoule 502 and then evacuate the ampoule to a vacuum of less than 1 mtorr and seal it shut next raise the temperature of the ampoule to about 600 700 u00b0 c for a short anneal about 1 hour this melts cd 508 cd melting point about 321 u00b0 c and vaporizes some cd.