First-principles Study Of Hydrogen-doped AlN And ZnO-based Diluted Magnetic Semiconductors

Recent years, diluted magnetic semiconductor materials have attracted a lot of research interests due to their unique properties and broad prospects for application. More and more theoretical and experimental scientists pay attention to them. In addition, hydrogen is abundantly and unavoidably present during the preparation process of AlN and ZnO-based diluted magnetic semiconductor materials. Moreover, the presence of hydrogen has a significant impact on material properties. Therefore, in this dissertation based on first-principles calculations the hydrogen-doped AlN and ZnO-based diluted magnetic semiconductor materials have been studied. The main contents are as follows:First of all, the research background were introduced, including the developments of semiconductor materials, spintronics, ZnO-based and AIN-based diluted magnetic semiconductor and the effect of hydrogen on the doped semiconductor material properties. Meanwhile, the details to the theoretical basis and implementation process of first-principles calculation involved in this thsis were also presented.Secondly, structural stability and vibrational properties of hydrogen-doped p-type AlN materials were investigated using first-principles methods. We studied the existence and bonding of hydrogen in the group-â…¡(Be, Mg, Ca, Sr, Ba)-doped AlN, and obtained the vibrational frequencies of relevant hydrogen complex which were significant to the experiment study. Furthermore, the calculated results indicate that the stability and vibrational properties are greatly influenced by the variation of the size of doped ion. Anharmonic effect on the vibrational frequencies, caused by the light quality of hydrogen, was taken into account. That ensured us to achieve accurate calculated results.Next, we turned to the Co-doped ZnO materials, the existence of hydrogen atoms, as well as electronic structure and vibrational properties were studied. The geometry of hydrogen and its bonding were investigated by the first-principles calculation. The results indicate that hydrogen is strongly formed with 0 atom, exhibiting+1 charged and acting as a donor. Taking into account the effect of anharmonic contribution, we studied the local vibrational mode (LVM) of O-H complex, and obtained the vibrational frequencies for hydrogen in its stable positions. Our results provide an essential theoretical suggestion for the experimental researchers to explore the existence of hydrogen and the preparation of p-type ZnO.Finally, first-principle calculation and Monte Carlo simulation were employed to study the Co-doped ZnO diluted magnetic semiconductor with hydrogen doped. Electronic structure as well as magnetic properties were investigated. The results reveal that hydrogen could lead to a change in electronic transfer, inducing the magnetic coupling changes, resulting in a Curie temperature above the room temperature.