II-VI族稀磁性半導體電子特性研究

Abstract

本論文使用第一原理總能計算程式CASTEP（Cambridge Series Total Energy Package）來進行II-VI族半導體ZnSe與CdSe在壓力下所產生的相變之模擬，得知ZnSe在壓力下會由Zinc-blende轉變為cinnabar相再轉變為rocksalt相，CdSe則直接由Zinc-blende轉變為rocksalt相。接著進行CdSe聲子效應的模擬，得知CdSe的LO與TO振動頻率和其振動模式。並模擬將Fe原子部分取代Cd原子而成的II-VI族稀磁性半導體Cd1-xFexSe的電子結構與能態密度，得知隨掺雜濃度x增加其單位晶格體積會減少，與其能態峰值的變化。

By using the program of CASTEP (Cambridge Series Total Energy Package) based on the first-principle theory, we have studied the phase transitions of ZnSe and CdSe under high pressure. The result shows that the structure of ZnSe will be transformed from zinc-blende to cinnabar, and become the rocksalt structure as the presssure is increased. It is found that the structure of CdSe is directly transformed from zinc-blende into rocksalt. And the frequencies and modes of LO and TO phonons in CdSe are obtained. Besides, we have also calculated the electronic structures and density of states of the DMS compounds Cd1-xFexSe which is resulted from the partial substitution of Fe into the site of Cd in CdSe. It is found the volume of the unit cell of Cd1-xFexSe decreases when the concentration fraction x is increased. The amplitudes and the positions of peaks of density of states are changed with respect to the fraction x.