GexSi1-x合金中的键长及其对电子能带结构的影响

采用经验紧束缚理论，以类似闪锌矿结构的晶体模型模拟Ge_xSi_1-x合金，根据总能最小原则计算了Ge_xSi_1-x合金中的键长及点阵常数．同时以紧束缚方法计算了原子位置发生弛豫前后的电子能带结构，并与虚晶近似下的计算结果进行了比较．计算结果表明，Ge_xSi_1-x合金中的键长基本上与合金组分无关，各自接近于Ｇｅ，Ｓｉ晶体中的键长，与广延ｘ射线吸收精细结构（ＥＸＡＦＳ）测量结果符合得 关键词：

THE BOND LENGTHS AND THEIR EFFECTS ON THE ELECTRONIC ENERGY BAND STRUCTURES IN THE GexSi1-x ALLOYS

Using the empirical tight-binding method, the bond lengths and lattice constants in the Ge_xSi_1-x alloys are calculated through minimizing the total energy in zincb-lend-like crystal models, with which the Ge_xSi_1-x alloys are simulated. With the tight-binding method the electronic band structures are calculated for the models before and after the atoms relax and the calculated results are compared with that obtained in virtual crystal approximation. The calculated results are as follows: The bond lengths in the Ge_xSi_1-x alloys generally do not depend up on the alloy compo-sition and nearly equal to the bond lengths in the Ge and Si crystals respectively. This result is consistent with the experiments quite well. The relaxation of atoms has little effects on the electronic band structures for the alloys. However, the chemical composition disorder plays the most important role in determining them.