Thermodynamic analysis and CVT growth of ZnSe single crystal

The thermodynamic properties of transporting reactions in ZnSe-I₂, -H₂, -HCl and -NH₄Cl chemical vapor transport systems were analyzed by solving sets of equations with numerical methods. The results show that ZnSe-NH₄Cl system has the properties of high total pressure and moderate reaction enthalpy change. The hydrogen (H₂) produced through decomposition of NH₃ is capable to adjust the transporting component partial pressure of H₂Se. Referring to the component partial pressure in ZnSe-I₂ system, the process parameters in ZnSe-NH₄Cl system are primarily selected for ZnSe single crystal growth. The concentration of NH₄Cl ranges from 0.5 to 1.0 mg/mL at the growth temperature of about 1000°C. An as-grown ZnSe single crystal is obtained with dimension of 8 mm × 6 mm × 4 mm. The full width at half maximum of X-ray double crystals rocking curve on (111) as-grown surface is 60.48″ and the etching pits density (EPD) is about (4.5-5.0) × 10⁴/cm².