| For a long time,Si has occupied a dominant position in semiconductor applications,however it is also facing the limitation of material scalability and development potential.In addition,with the chip size decreasing a lot,it may approach the limit of Moore's law.More and more attention would be paid to the research of new materials,new technologies and low energy consumption semiconductor devices.As a new generation of semiconductors,Ga2O3 has an ultra-wide band gap and higher critical breakdown field.And low-cost,large size and high-quality single crystal substrates can be obtained by using traditional crystal growth methods.Now it has present good performance in Schottky barrier diodes and field effect transistors(FETs),so it is expected to play a greater potential in the future photoelectronic devices.The Schottky barrier(SB)is important to evaluate the charge transfer efficiency at the metal-semiconductor interfaces.Lower SB means smaller contact resistance and lower energy consumption,which is key to the preparation of Ga2O3 devices with excellent performance.However,both experimental and theoretical studies on Ga2O3/metal interface are still in progress,especially theoretical research is very limited.Some experiments have shown that single layer graphene or BN inserting can effectively reduce SB between interfaces,however,reports on Ga2O3 sandwich structure are still limited.In this project,we mainly studied the SB between Ga2O3(100)and different metal interfaces,and the effect of BN intercalation on the SB.In addition,the Ga2O3/Al2O3 alloy system has been studied.The specific research contents and results are as follows:(1)Analysis of Schottky barrier between Ga2O3 and different metalsIn this paper,the Schottky barriers at the interfaces between Ga2O3 and Mg,Ni,Pd,Cu and Pt metals are studied by performing first-principles method.The lowest SB(0.23 eV)at the Ga2O3-Mg interface is calculated by means of layered partial density of states and wavefunction validation,which is significantly lower than the other four Ga2O3/metal interfaces(1.06-1.39 eV).The effects of interfacial structure,metal induced gap states and metal work function on SB are analyzed.The results show that Ga2O3 is not significantly regulated by metal work function,because metal induced gap states lead to Fermi-level pinning.The tunneling barriers and tunneling probabilities at five interfaces are calculated.The results show that Mg interface has a higher tunneling probability and better tunneling efficiency.(2)Influence of inserting BN on Ga2O3 Schottky barrierWe studied the effect of single-layer h-BN interlayer on the SB at Ga2O3 interfaces.The results show that the BN layer insertion has a dramatic effect on the SB.For Ga2O3/Au interface,BN insertion can significantly reduce the SB and even form an ohmic contact.Conversely,the SB is increased for near-ohmic Ga2O3/Mg system.However,the tunneling barrier disappears and perfect electron tunneling transmissions show.Both of their local density of states show that the insertion of BN can effectively prevent the generation of metal-induced gap states,and thus affect the results of SB.(3)Study on(AlxGa1-x)2O3 alloyThe stability of the monoclinic and corundum phase of Ga2O3/Al2O3 alloys at different doping concentrations was studied.Disordered(AlxGa1-x)2O3 alloys was simulated by special quasirandom structure method(SQS).The structural phase transition point was obtained,and the band gap change of gallium aluminum alloy at different concentrations was calculated.The results obtained above are consistent with the reported experimental results.Through these results and discussions,we can have a further understanding of the theoretical mechanism of the SB between Ga2O3 and metal interfaces,and provide important theoretical basis and guidance for the design and development of Ga2O3 electronic devices. |
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