Crystal growth and characterization of CdTe grown by vertical gradient freeze

In this study, crystals of CdTe were grown from melts by the unseeded vertical gradient freeze method. The thermal history of the melt and the thermal gradient at the growth interface were adjusted to optimize the crystalline quality of the grown crystals. The grown crystals were studied by various characterization techniques, including synchrotron white beam X-ray topography (SWBXT), chemical analysis by glow discharge mass spectroscopy (GDMS), low temperature photoluminescence (PL) and Hall measurements. The SWBXT images taken from various angles show grains with inhomogeneous strains, nearly strain-free grains, as well as twinning nucleated in the shoulder region of the boule. The GDMS chemical analysis shows the contamination of Ga at a level of 3900 ppb, atomic. The low temperature PL measurement exhibits the characteristic emissions of a Ga-doped sample. The Hall measurements show a resistivity of 1 × 107 Ω cm at room temperature and 3 × 109 Ω cm at 78 K with the respective hole and electron concentration of 1.7 × 109 and 3.9 × 107 cm−3 at room temperature.