Optical and transport properties of chromium-doped CdSe and CdS0.67Se0.33 crystals

CdSe crystals were grown by the seeded physical vapor transport method with helium on CdS0.67Se0.33 seeds. A CrSe source was used for doping of both the CdSe and CdS0.67Se0.33 seed crystals with chromium during growth. An absorption peak in the near-IR range of 1.5–2.2 μm associated with the intracenter 5T2→5E transitions of Cr2+ ions was realized. The Cr2+ concentration in the various samples was calculated using the experimentally obtained peak values of the absorption coefficients, and it was found to vary from 1017 to 3×1018 cm−3. A ‘blue’ shift of the Cr2+-related near-IR absorption band maximum in CdS0.67Se0.33 relatively to the CdSe matrix was demonstrated for the first time. The measured Hall mobility of charge carriers in CdSe crystals with Cr concentration at a level of 2×1018 cm−3 reached a maximum value of 6000 cm2/V s at 50 K.