GROWTH OF 11 DOPED PbTe SINGLE CRYSTALS BY THE TRAVELLING HEATER METHOD

The travelling heater method (THM) has proved zone and the doped feed material (all 12 mm to be a suitable technique to grow highly perfect diameter) was put into a silica ampoule. The single crystals in a great variety of compounds, evacuated and closed ampoule was placed in a especially of Il—VI and Ill—V compounds. It offers small vertical resistance heater without any afterinteresting advantages such as higher homogeneity heater or similar equipment which allowed good in composition and lower growth temperatures, observation during growth. With a zone temperaleading to lower concentrations of lattice defects ture of about 550°C, the initial Te zone doubled and impurities, its length to about 10 mm according to the phase Only a few attempts at growing lead chaldiagram which is characterized by the PbTe concogenides or lead tin chalcogenides, the most imgruent melting point of about 924°C and an portant IV—VI compounds for optoelectronic deeutectic composition with 85.5 at% Te at 405°C. vices, have been tried by this method [1—4].There The average temperature gradient at the has been a certain interest in thallium doped PbTe solid—liquid interface was measured to be apas a substrate material for lead tin telluride laser diodes [5,6]. We prepared TI doped PbTe single crystals of high structural perfection, i.e., without lowering ~ low-angle boundaries which have been shown to mechanism usually result with Bridgman grown crystals of the same material [7]. siUca PbTe was synthesized in evacuated silica 0mp0~ ampoules from SN materials at about 1000°Cwith Tidoped a tellurium excess of 0.5 at%. It was followed by a PbTe feed normal freezing procedure to prepare the feed material. Together with the synthesized PbTe, the ampoule was charged with 0.5 at% SN thallium to resistance dope the source material for use by the THM heater-~ method. During melting the excess of tellurium re lawn I