Czochralski growth of CdTe and CdMnTe from liquid encapsulated melts

• Published in: Journal of crystal growth 1987-11, Vol.85 (3), p.510-520
• Main Authors: Hobgood, H.M., Swanson, B.W., Thomas, R.N.
• Format: Article
• Language: English
• Subjects: Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Growth from melts; zone melting and refining; Materials science; Methods of crystal growth; physics of crystal growth; Physics
• ISSN: 0022-0248; 1873-5002
• DOI: 10.1016/0022-0248(87)90484-2

CdTe and CdMnTe boules with diameters up to 50 mm and weighing up to 1 kg have been grown by liquid-encapsulated Czochralski (LEC) pulling from B 2O 3-encapsulated melts. The severe heat-transfer problems associated with the low thermal conductivity of CdTe were circumvented by suitable modification of a high-pressure Melbourn puller to accomodate > 400°C/cm axial gradients, convex radial temperature distributions at the encapsulant/melt interface, and helium overpressures of 75 atm. LEC CdTe boules were always characterized by a high incidence of twinning and polycrystallinity. However, by alloying with manganese at compositions up to 0.20 mole fraction MnTe, growth proceeding by means of alternating bands or lamellas perpendicular to the 〈111〉 growth axis was achieved. The lamellae consisted of twinned {111} sections of crystal corresponding to twinning on the (111) plane perpendicular to the pulling direction. These crystals exhibited semiinsulator behavior, dislocation densities in the 10 5 to 10 6 cm -2 range, and subgrain misorientations within the twin lamellae of 300 arc sec to 1° from the 〈111〉 growth direction. The major chemical impurity incorporated in these growths was boron in the form of electrically inactive inclusions presumably associated with the encapsulant. Preliminary attempts to control melt convection by the application of magnetic fields to LEC CdTe and CdMnTe melts indicate that field intensities much greater than 2000 G will be required.