First Principles Study Of The Interface Characteristics Of Metal-monolayer GaS Heterojunctio

GaS is a new type of two-dimensional semiconductor material that has emerged in recent years.It has received attention from researchers for its peculiar physical and chemical properties and has been widely used in many fields,such as field-effect transistors,photodetectors and photodiodes,opening a fascinating door to nanoelectronics.The application of two-dimensional semiconductors inevitably involves contact with metals,so it is essential to study the contact between metals and two-dimensional GaS semiconductors.In this thesis,the interfacial properties of three-dimensional metal-GaS heterojunctions,the modulation of the Schottky barrier at the interface of Ni-GaS heterojunction by halogen group element doping and the interfacial properties of MXene-GaS heterojunctions are investigated based on the first principles calculations.The results of the calculations in this thesis are as follows:（1）The interfacial properties of metal（Ni,Cu,Zr,Pd,Rh,Hf,Ir,and Pt）tangential-monolayer GaS heterojunctions were investigated,and the properties of interfacial binding energy,electrostatic potential,and differential charge density of the eight heterojunctions were mainly calculated.The results show that the interaction between the heterojunction interfaces formed by metals Ni,Cu,Pd,Rh,Ir and Pt with GaS is weak,and n-type Schottky contacts are formed at the vertical interface（at interface B）,while the interaction between the Zr-GaS and Hf-GaS heterojunction interfaces is strong,and GaS is severely metallized,leading to the disappearance of the Schottky barrier at the vertical interface and the formation of an n-type Schottky contact at the horizontal interface（at interface D）n-type ohmic contact.The ohmic contact facilitates the efficient carrier injection,so the metals Zr and Hf are more suitable for the electrode materials of GaS.（2）The effects of doping with halogen group elements（F,Cl,Br and I）on the electronic properties of monolayer GaS and the modulation of the Schottky barrier at the Ni-monolayer GaS heterojunction interface are investigated.The results show that the halogen-doped GaS systems all introduce impurity energy levels at the Fermi energy level,and all are n-type doped,which enhance the electrical conductivity of GaS.The reduction of the Schottky barrier is conducive to the efficient carrier injection,which is of great importance for the fabrication of high-performance Schottky devices.（3）The interfacial properties of six MXene（Cr₂C,Hf₂C,Mo₂C,Ta₂C,Ti₂C and V₂C）-GaS heterojunctions are investigated.The calculated results show that the interfaces of metal Cr₂C,Ta₂C and V₂C-GaS heterojunctions form n-type Schottky contacts.The interfaces of metal Hf₂C,Ti₂C and Mo₂C-GaS heterojunctions form n-type ohmic contacts,indicating that Hf₂C,Ti₂C and Mo₂C are more suitable as metal electrode materials for GaS.