Study Of Photoelectric Properties Of Silicene On ?-? Semiconductor Substrates

Silicene,similar to honeycomb structure graphene,is a two-dimensional monoatomic layer silicon film.Nowadays,it has become one of the research hotspots of graphene like two-dimensional materials.The single-layer silicene has an adjustable band gap,which solves a basic problem of graphene with zero bandgap.Its greatest benefit is that it can be compatible with the existing silicon-based semiconductor technology,and has a great application prospect in the field of semiconductor electronic devices and optoelectronic devices in the future.However,the silicene can not exist independently,it needs to be supported by substrate materials.Generally,the silicene are grown on metal substrate in experiments,but the metal substrates could produce strong orbital hybridization with the silicene layer,which leads to the loss of Dirac cone characteristics of silicene.Therefore,it is an important topic to find a suitable semiconductor substrate for the epitaxial growth of silicene and study the optoelectronic properties of silicene/semiconductor heterostructure,which is of great significance to the experimental preparation and the devices development of silicene.In this thesis,the stability,electronic properties and optical properties of silicene on?-?semiconductor substrates are studied by first principles calculations based on density functional theory.The following research results have been achieved:1.The stability and electronic properties of sicene on GaAs(111),GaP(111),AlAs(111)and Ga N substrates are studied.By introducing hydrogen intercalation,the interaction between silicene and substrate surface are weakened.The results show that silicene can exist stably on GaAs(111),GaP(111)and AlAs(111)substrates,but the structure of silicene on Ga N substrate is seriously distorted.The buckling heights of silicene on the anionic surfaces of GaAs(111),GaP(111)and AlAs(111)substrates are0.467-0.488(?),and 0.611-0.650(?)on the cationic surfaces.From the perspective of experimental growth,the low buckling height of silicene on the anion surface of semiconductor substrates is more conducive to silicene growth.Because the interaction between the silicene layer and the substrate surface are weakened by the hydrogen intercalation,silicene open direct bandgap of?0.2 eV on anion surfaces and indirect bandgap of 0.41-0.62 eV on cation surfaces.Anionic surface substrates can provide effective mechanical support for silicene without disturbing its atomic structure.2.Considering the excellent properties of silicene on GaAs(111)substrate,we deeply investigate the electronic properties under external field and optical properties of silicene/HGaAs heterostructures.The results show that the electronic properties of the silicene/HGaAs heterostructure can be controlled by adjusting the layer spacing L_zand buckling height d,applying biaxial strain?and external electric field F.With the modulation of L_zand d,the maximum bandgap is 0.23 eV of silicene/HAs-GaAs heterostructure and 0.65 eV of silicene/HGa-GaAs heterostructure,and it happens transitions between direct and indirect bandgap.By adjusting?,the maximum bandgap is 0.25 eV of silicene/HAs-GaAs heterostructure and 0.58 eV of silicene/HGa-GaAs heterostructure.However,silicene/HAs-GaAs and silicene/HGa-GaAs heterostructure can bear only a small range of strain,and larger biaxial strain will lead silicene to loss bandgap and transform into metallic properties.It can adjust the bandgap,but can not make the bandgap open larger by applying electric field.Moreover,the silicene/HGaAs heterostructures are sensitive to the reverse vertical electric field,and they are easy to lose the bandgap and become metallic.In addition,through the analysis of the optical properties of silicene/HGaAs heterostructures,it is found that there are multiple absorption peaks in the energy range of 1-12 eV,and the heterostructures have typical optical properties of free-standing silicene.3.The equivalent and nonequivalent intervalley scattering of silicene on As-terminated GaAs(111)substrate are studied by using density functional theory and deformation potential theory based on first principles.The calculated intervalley scattering rate of silicene/HAs-GaAs is?10¹²s^-1,which becomes the main scattering mechanism.The intervalley scattering of silicene on As-terminated GaAs(111)substrate is insensitive to the change of temperature,and the scattering processes of emitted phonons play a dominant role.We also studied the effects of the buckling height d of silicene and the distance L_zbetween silicene and substrate on the intervalley scattering.Changes in the buckling height d of silicene and the distance L_zbetween silicene and the substrate have a negligible influence on the equivalent intervalley scattering between K valleys but have a great influence on the non-equivalent intervalley scattering from the K valley to(38)valley;however,these changes in scattering rates are within an order of magnitude.Therefore,fluctuations in the buckling height d of silicene and the distance L_zbetween silicene and thesubstrate have a certain effect on the intervalley scattering in the process of experimental growth and device manufacturing.This study provides theoretical support for the transport properties of silicene on semiconductor substrate and verifies the importance of intervalley scattering.It provides theoretical guidance for the growth of silicene on semiconductor substrates and the fabrication of devices.In this thesis,there are 37 pictures,2 tables and 218 references.