【作者】 李春彦；

【导师】 王锐；

【作者基本信息】 哈尔滨工业大学 ， 工业催化， 2006， 硕士

【摘要】 砷化锗镉晶体(CdGeAs2)是黄铜矿类半导体晶体中综合性能最优者,其非线性光学系数和远红外区透过率很高,但其在中红外区5.5μm有较强的吸收。本论文主要采用水平梯度冷凝法生长CdGeAs2单晶,运用密度泛函理论的平面波赝势法计算了砷化锗镉晶体及砷空位、锗占砷位-砷化锗镉晶体的结构、能带结构、态密度、光学性质等,提出了铬掺杂砷化锗镉晶体能有效的降低红外吸收。首先通过大量的实验研究选择合适的工艺条件合成砷化锗镉多晶,在具有较低温度梯度的水平单晶炉中生长CdGeAs2单晶,同时填充氩气以抑制砷的挥发。生长出的单晶粉末做XRD衍射分析检测,发现其X-射线衍射图与标准图谱相一致。用红外光谱仪在中红外区做吸收检测,结果显示晶体在中红外区的吸收较低。运用密度泛函理论计算,建立纯砷化锗镉晶体的结构模型并对之进行结构优化,使理论模型更加接近真实结构,从而研究纯砷化锗镉晶体的能带结构和态密度、光学性质;分别建立砷空位模型(VAs-CdGeAs2),锗占砷位模型(Ge/As-CdGeAs2),分别计算它们的能带结构、态密度、光学性质。同时计算了铬离子掺杂模型的能带结构,推断出铬掺杂砷化锗镉晶体能改变晶体的能带结构,降低红外吸收。通过能量优化,锗占砷位缺陷的能量最接近理想的纯砷化锗镉晶体优化能量,这与EPR对缺陷检测结果相一致,所以锗占砷位反位缺陷是最可能的吸收缺陷。更多还原

【Abstract】 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.更多还原