Growth Of Single-CdGeAs₂ And Research By Density Functional Theory

Cadmium germanium arsenide, CdGeAs2, has promising advantage for its attractive nonlinear optical properties in all chalcopyrite semiconductors. It has an extremely high nonlinear coefficient, a wide infrared transparency range, but crystal of CdGeAs2 has a strong absorption at 5.5μm which related to a native acceptor-defect. With the use of the horizontal gradient freeze technique, crack-free single crystal can be produced eventually. We calculate pure CdGeAs2 and all the possible model of defect-CdGeAs2 with the use of density functional theory. Donor impurities (e.g., Cr2+) can compensate acceptors for the decrease in the absorption in infrared transparency range.Polycrystalline was produced in good technical temperature through a lot of experiments. Single crystal growth chargng an overpressure of 1 atm argon to suppress vaporization of Cd and As. The diffraction patterns of singled produced is very agree with the standard graph of CdGeAs2. Absorption spectra measured between 2.3 to 18μm, the absorption coefficient was low for use.Firstly, structure model of pure CdGeAs2 was upbuilded, moreover the structure was optimized so that it was very similar to real structure. Consequently, the energy band structure and the densities of state were researched. Secondly, VAs-CdGeAs2 and Ge/As-CdGeAs2 were upbuilded. After Geometry Optimization, their energy band structure, densities of states were calculated and analysised. We also calculated the model of doping Cr,which can change the energy band structure of CdGeAs2, the result is valuable for decreasing optical absorption.Through the energy analysised, it was suggested that a germanium-on-arsenic anti-site defect was the most possible defect which may be associated with the 5.5 micron absorption, the result of analysis are agreement with the research of EPR, so the calculates are accurate.