In order to be used as γ-detectors, CdTe single crystals have to be of high resistivity and must possess a high level of perfection and be free of linear as well as volume defects.
The present research presents a new method of CdZnTe single crystals growth with natural faceting by vapor transport using a polycrystal ingot as initial source material. Source polycrystal Cd0,96Zn0,04Te1+-δ (δ = 0,0001) or Cd0,87Zn0,13Te0,999 ingots were synthesized by melting together calculated amounts of elementary components
CdxZn1-xTe single crystals were grown in a 35 mm diameter quartz ampoule located in an isothermal medium at 1050-1150 K. The temperature gradient along the ingot was built owing to thermal radiation. By use of a capillary tube the redundant component is removed from the growth zone and deposited in the cold zone. The single crystals growing rate reached as high as 2 cm3/day. As a result, we obtained single crystals with 2,5x2,5x4 cm3 dimensions, constrained by natural faces corresponding to the (110), (100) and (111) planes, the dislocation density being ~103 cm-2.
Measuring of the rocking curves half-height width for reflection planes (CuKα X-radiation) with Miller indices (111), (220), (311), (422) and (331) gave 25.0 s, 17.5 s, 13.6 s, 20.8 s and 13.6 s values respectively. X-ray patterns obtained in CuKα radiation do not reveal any volume defects or mechanical stresses.
Crystals of both n- and p-type were obtained, carrier concentration being at 300K n =3x1014/cm3 or p =1,7x1015/cm3, with carrier mobility of 326 cm2/Vs, 69 cm2/Vs respectively.
Using as source substance a Cd0,96Zn0,04Te1,0001 alloy with 0,2 mol% of Ga2Te3 single crystals by vapor transport could be grown. They possess a 2x106 Ohm cm resistivity at 300 K.