THE PROPERTIES OF (PB,GE)TE SINGLE-CRYSTALS GROWN FROM THE VAPOR-PHASE

Single crystals of Pb1-xGexTe solid solutions were grown from the vapour phase over the whole composition range. The properties of the samples were examined using electrical methods (Hall concentration and mobility), microprobe and X-ray single and powder diffractometry at 20-400-degrees-C. Except for the case of x = 0, the samples were p-type with increasing hole concentration for higher GeTe content. The crystals with low GeTe content exhibited high crystallographic perfection, which decreased as the value of x increased. This was caused by a transformation from cubic to rhombohedral structure when the crystals were cooled after the growth process. For crystals with x < 0.5, the rhombohedral angle was smaller than the one measured using powder diffractometry. This can be attributed to the blocking of the phase transition by the cubic cell elongation in different [111] directions.