Theoretical Study On Properties Of Gallium Oxide Materials And Transistors

In recent years,the third-generation semiconductor has gradually become the focus of semiconductor technology development.Because the third-generation semiconductor has the advantages of high frequency,high voltage resistance,high temperature resistance and so on,these properties are not only applicable in high power devices,photoelectric detection,gas sensing sensors and so on,but also make the third-generation semiconductor have the potential to become the key materials to support the new generation of mobile communication,new energy vehicles,high-speed trains and other industries.Among them,the?-Ga₂O₃ has a larger band gap and higher breakdown field strength than other third generation wide band gap semiconductors,and the properties like ultrahigh Baliga's figure-of-merit make it more significant in terms of high-power devices.However,the previous study found that the experimentally prepared?-Ga₂O₃ device performance was much lower than theoretically expected.One important reason is that the Ga₂O₃ device performance is directly related to the electrode metal/Ga₂O₃ interface,and the non-ohmic contact electrode metal/Ga₂O₃ interface has large interfacial resistance and Schottky barrier,which can seriously affect the charge transport at the electrode metal/Ga₂O₃ interface and the thermal breakdown effect of the Ga₂O₃ device.Therefore,improving the material properties of Ga₂O₃ and the interface performance of electrode/Ga₂O₃ are very important for achieving high-performance Ga₂O₃ devices.In this thesis,the structural,electrical and mechanical properties of?-Ga₂O₃ are studied by first-principles calculation method.The electrode metal/Ga₂O₃ interface model is established and analyzed,and to improve the interfacial properties,a two-dimensional material is proposed as the intermediate intercalation modified electrode metal/Ga₂O₃ interface and its properties are investigated.The main research results are as follows:1.Similar to previous reports,the bond length of the Ga₁-O₁ bond in the?-Ga₂O₃ cell is greater than that of the other Ga-O bond,and the electron effective mass is about 0.23?0.28m₀.The 13 independent elastic constants of?-Ga₂O₃ conform to the mechanical stability criterion,their thermodynamic properties have obvious anisotropy,and the elastic constants C₄₄ are smaller than C₅₅ and C₆₆,which indicates that it is easier to cut in the direction perpendicular to a.The bulk modulus B,shear modulus G,Young's modulus E,and Poisson's ratio?were measured by Voigt-Reuss-Hill method.the B/G and?values of?-Ga₂O₃ are greater than 1.75 and 0.26,respectively,indicating the ductility of?-Ga₂O₃.2.The metals Sc,Al,Ti,Ag,Au,Pd,Pt with seven different work functions were selected as the electrode,and the electrode metal/Ga₂O₃ interface model was established.The contact interface of metal and channel material in the transistor was divided into two interface studies:A and B,and the results show that the surface of Ga₂O₃ directly in contact with the metal was all metalized.The barrier at interface B is calculated by the method of deep energy level alignment.The metals Sc,Al,Ti and Ga₂O₃ interfaces with smaller work functions form an ohmic contact.The barrier height at the interface between metal Ag and Ga₂O₃ is only 0.06e V different from the fermi level.The n-type Schottky barrier exists at the interface formed by the metals Au,Pd,Pt and Ga₂O₃ with the larger work function and Ga₂O₃,and the sizes are 0.51 e V,0.61 e V,0.58 e V,respectively.The fermi pinning factor on the surface of Ga₂O₃is 0.56.The study found that the formation of chemical bonds between metals and Ga₂O₃weakened the Ga-O bond on the surface of Ga₂O₃,allowing the orbitals of the Ga and O atoms to extend into the band gap to form the interface state.3.A Metal/2D-materials/Ga₂O₃ interface model with two-dimensional materials graphene and boron nitride(BN)as intermediate intercalation was established.Using the same seven metals as electrodes,the study found that both the intercalated graphene and BN were metallized.For the metal/Ga₂O₃ interface,it was found that the Schottky barrier height of the interface after adding graphene as the intermediate layer did not decrease significantly and the fermi pinning effect was enhanced.On the contrary,with the addition of BN as the intermediate layer,the barrier of the entire interface is significantly reduced,and the barrier height is lower than 0.1 e V,but the case of complete pinning appeared.The above shows that the addition of two-dimensional material intercalation was beneficial to reduce the barrier height of the metal/Ga₂O₃ interface under specific conditions.