A new growth method for CdTe: A breakthrough toward large areas

CdTe and CdZnTe are well-investigated II-VI semiconductors, mainly used as substrates for the HgCdTe-IR detection and as detectors for x-ray and γ-ray detection. For both applications, the demand is toward larger and larger dimensions to make larger infrared (IR) and x-ray and γ-ray arrays. This paper presents a new method to grow large dimension CdTe (or CdZnTe), mainly devoted to x-ray and γ-ray detection. This method is based on solvent evaporation from Te-rich solution made of cadmium and tellurium (optionally zinc); it operates in an open tube, and growth proceeds in a crucible maintained at a constant temperature. At the end of growth, a disc of CdTe (or CdZnTe) is obtained, the thickness of which is in the range 1–10 mm. The 65-mm-diameter discs appear as polycrystals with large grains. The electrical properties strongly depend on the presence of voluntarily introduced dopants to obtain high-resistivity material. Two different impurities are commonly used to obtain resistivity in the 10¹⁰ Ωcm range: aluminum and chlorine. Characterization of both doped materials and results of detectors under x-ray and γ-ray illumination will be given; spectrometric grade performance has been obtained and will be presented. The originally 65-mm-diameter crucible can be scaled up to 300 mm in diameter; this will be discussed in the paper.