The Preparation of Graded‐Band‐Gap Single Crystals of II–VI Compounds

Graded‐band‐gap single crystals of ZnxCd1−xSe, CdS1−xSex, CdSe1−xSx, Zn1−xCdxS, and ZnxCd1−xSySe1−y with x and y increasing along the direction of growth have been prepared by two different vapor phase methods. Typical crystal dimensions in the systems CdS1−xSex and CdSe1−xSx are 6 × 7 × 20 mm3, in the other systems 2 × 3 × 8 mm3. The gradient of the band gap in the system CdS1−xSex could be varied between 0.1 and 2.0 eV/cm. The change in band gap vs. crystal position was determined by absorption measurements. All crystals show edge emission at liquid air temperature under excitation by uv light.