Investigation of structural electronic and vibrational properties of III-N materials and beryllium chalcogenides

The aim of this thesis is to investigate structural, electronic and dynamical properties of III-nitride materials (BN, AlN, GaN and InN), Beryllium-chalcogenides (BeS, BeSe and BeTe) and their (110) surfaces, theoretically. These properties of the zinc-blende bulk phase and the (110) surface of III-nitrides and Be-chalcogenides have been studied by employing the plane-wave pseudopotential method, density functional theory, linear response technique and supercell approach. The reason for choosing this topic is that these materials are very suitable for applications in electronic, opto-electronic and semiconductor devices because of their large band gaps and hardness. Due to these interesting properties, there has been great interest in the study of bulk properties of these semiconductors. Although the ground state properties of these materials are well understood now, studies of structural, electronic and vibrational properties of their surfaces are fewer and incomplete. In particular, theoretical or experimental investigations of Be-chalcogenide (110) surfaces are still lacking from the literature. Thus, it is important to determine structural, electronic and vibrational properties of these semiconductors and their (110) surfaces in order to succesfully apply them to technological devices.In the first four chapter of this thesis, previous studies, crystal structures of these semiconductors and their surfaces, experimental techniques and density functional theory have been explained. In the fifth and sixth chapter, we have presented our structural, electronic and vibrational results for bulk III-N materials and Be-chalcogenides, respectively. The same properties of III-N(110) surfaces are presented and widely discussed in the chapter seven. In the chapter eight, investigations of BeS(110), BeSe(110) and BeTe(110) surfaces have been presented firstly in the literature. In the last chapter, our results have been discussed as well as the possible future works.