Structural and optical properties of oxygen doped single crystal ZnTe grown by multi-tube physical vapour transport

Abstract

Bulk single crystals of zinc telluride up to 10 mm thick have been grown by the Multi-Tube Physical Vapour Transport technique and doped, in-situ during growth, with oxygen. Following hetero-epitaxial nucleation and buffer growth on 100 mm diameter GaAs seed wafers, oxygen was introduced to the quartz growth envelope, using nitrous oxide as a precursor, via a novel gas injection system. Mass spectra from a residual gas analyser sampling the gases exiting the growth envelope indicated that the nitrous oxide had been cracked at the operating temperature of the furnace releasing oxygen into the growth region. The structural perfection of the grown crystals was assessed by synchrotron based X-ray diffraction measurements and found to be extremely high, improving significantly with distance from the seed. Rocking curve widths, measured over a 4 mm × 7 mm area, as low as 20 arcsec were observed. No evidence was found for a reduction in crystalline quality resulting from the incorporation of oxygen. Luminescence studies (4–300 K) showed strong red luminescence at 680 nm persisting up to room temperature indicating that oxygen had been incorporated substitutionally onto tellurium sites. This material is highly transparent at the red emission wavelength with absorption coefficients of approximately 2 cm⁻¹. Under alpha radiation from a ²⁴¹Am source, scintillation was observed from the doped material with approximately 12,700 photons/MeV and a full width at half height maximum of 27%. The material is a potential candidate for large volume scintillation based radiation detectors.