Valence Electron Structure And Physical Properties Of Several Typical Semiconductor Materials

The study on semiconductoring material is one of active topics due to its application on IT industry. In recent years, it have attracted a great deal of attention due to the property on energy conversion from solar energy to electric power. It reveals new application of semiconductor on solar cells. According to the previous studies on both theoretical and experimental researches, the empirical electrionic theory (EET) is used to study these special characteristics of these semiconductors. The relations between the valence electroin structures and properties are studied for understanding the origin of physical properties. The results could be concluded as follows:1. The hybrid states of Ge and Si are at the 6th level with covalent electron pairs of nc=0.97 and Pauling of 0.71. The calculated cohensive energies of Gd and Tb are 464 kJ/mol and 384 kJ/mol, respectly, which agree with experimental values 446 kJ/mol and 372 kJ/mol, respectly.2. For pure Gd and Tb, the valent electronic distributions of s,p,d electrons are similar without considering 4f electrons, which can be used to explain the similarity of physical properties. The calculated results of cohesive energy shows that the contribution of 4f electrons to cohesive energy of Tb is more significantly than that of Gd, which means that the 4f electrons of Tb is more easily to be bonding. According to the Hund rules, the 4f electrons of Gd is half full which is responsible for the hardness of bonding of 4f electrons.The theoretical calculations reveal that the contributions of 4f electrons to melting points for both Gd and Tb can be omitted. Since magnetic electrons arrange disordered at a high temperature closing to their melting points, the influence of 4f electrons of Gd and Tb on melting points is small.3. EET analysis reveals that the hybrid states of Cd and S atoms in wurtzite and zinc blende structures of CdS are both on the 4th levels. Since the samiliarityof electron distributions and bond energies for Cd and S in the two structures, the cubic and hexagonal phase coexist in CdS single crystal. The theoretical value of cohesive energy of wurtzite is larger than that of the zinc blende structure, so the wurtzite structure of Cd is more stable.On the basis of the values of various bonds, the long bonds of Cd-S, Cd-Cd and S-S with lower bond energies are easy breaken,while the strong bonds which are not parallel to c-axis are likely to rotare, so phase transition occours with high pressure condition.All above shows that phase transition of wurtzite is due to the broken of weak bonds and the rotation of strong bonds, which orign from the crystal anisotropy.4. The studying results of ZnO:The lattice electrons of ZnO are only offered by the 4s electrons of Zn atom, which agree with the results of frist principles. Compared with the electron distribution of 13th hybrid level of single crystal Zn(s1.1689 P2d1.1689), the Zn atom of ZnO is on the 4th hybrid level, the valence electron contribution is s1.8877p2d1.8877, the electron number of 4s and 3d become larger, which suggests that oxidation results in the transfer of a part of 3p electrons to the 4s and 3d electrons. According to EET, the doping type is determined by the number of valence electron electrons of doping atom.