The First-Principles Study Of Electronic Structures And Properties Of ZnO

Zinc oxide (ZnO) is a kind of direct wide band-gap semiconductor material which is used widely and has many excellent properties. Structures and properties of the material can be well designed and constructed. Based on the first-principles method, the native point defects, the doping of other elements in ZnO, electronic structural and optical properties under the condition of extental force on ZnO are studied and analyzed.There are three parts in the dissertation. The first part concentrated on the study on 4 sorts of electronic structures about native point defects which had lots of divarications about accurate enegy levels and which had complex mechanism in ZnO. The second part concentrated on the the effect of unintentional doped H and C in ZnO and the analysis of doped Na in ZnO in which is difficult to realize p-type conversion and of doped Al in ZnO in which is difficult to judge the site on the lattice or in the interstitial gap. The last part concentrated on the effect of the electronic structures and optical properties under extental force on ZnO. The main contents are as the following:1. We calculated electronic structures of perfect ZnO and ZnO with native point defects such as Oi (interstitial O), Zni (interstitial Zn), VZn (vacant Zn) and Vo (vacant O). The results indicated that ZnO was a kind of direct band-gap semiconductor material. Oi produced an acceptor level while Zni showed a new donor lever bellow the bottom of the conduction band. VZn produced an acceptor level on the top of the valence band, while Vo produced a deep donor level below the bottom of conduction band and a deep donor level had obvious local phenomenon. On the basis of results, we confirmed that Zni was the main factor to induce n-type conductivity in ZnO.2. Unintentional doped H and C, doped Na and doped Al in ZnO were calcucated and analyzed. The results indicated:(1) the unintentional doped H had two stable sites and formed H-O while the unintentional doped C can destroy the lattice on ZnO. (2) The simple doped Na was difficult to realize p-type conductivity in ZnO while Zni and Nai had the role of strong compensation of Na on the lattice in ZnO. (3) The study on the different doping mechanism about Al in ZnO. The conclusions revealed that interstitial Al caused the formation of deep donor level, while substitute Al producted shallow donor level and broadened optical absorption edg.3. The affect on electronic structures and optical properties of Wurtzite ZnO under different extental force was calcucated and analyzed. With the increase of stress on ZnO, the results showed that (1) volume of ZnO became small and band gap became wide; (2) the valence band moved to low energy level; (3)the peaks in absorption, reflectivity, refractive index, dielectric function and loss function moved to high energy level.