A new growth method for CdTe: a breakthrough towards 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- and γ-rays. For both applications, the demand is toward larger dimensions to make larger IR and X- and γ-rays arrays. This paper presents a new method to grow large dimension CdTe (or CdZnTe), mainly devoted to X- and γ-rays 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; 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 get high-resistivity material. Two different impurities are commonly used to get resistivity in the 1010 Ω cm range: aluminium and chlorine. Characterization of both doped materials and results of detectors under X- and γ-rays illumination will be given; spectrometric grade performance has been obtained and will be presented. The original 65 mm diameter crucible can be scaled up to 300 mm in diameter; this will be discussed in the paper.