Mechanism Study Of Ohmic Contact To Ti/β-Ga₂O₃ Interface

β-Ga₂O₃ is a semiconductor material that has attracted widespread attention in recent years,with an ultra-wide bandgap as high as 4.6-4.9 e V,which makes it widely used in power devices,solar-blind UV detectors,high-power power electronic devices,gas sensors and other devices.application prospects.However,the structure and conduction mechanism between the contact interface between metal andβ-Ga₂O₃ have not been clearly studied.This paper takes metallic Ti andβ-Ga₂O₃ materials as the research goals,starting from the basic physical properties ofβ-Ga₂O₃ materials.Firstly,the Ti/β-Ga₂O₃ materials with ohmic contact are prepared by magnetron sputtering and rapid thermal annealing,and then from In terms of experiments,the samples with Schottky contact before annealing and the samples with ohmic contact after annealing were compared and tested,and the specific contact resistance of the samples with ohmic contact was tested at the same time.In terms of theoretical calculation,the formation mechanism of ohmic contact was explored.The main research contents and conclusions are as follows:1)Use the DC magnetron sputtering method to deposit Ti（～50 nm）and Au（109 nm）as electrodes on theβ-Ga₂O₃ substrate,and perform rapid thermal annealing on the samples under different annealing temperature conditions in nitrogen atmosphere,The annealing time was fixed at 120 s.After I-V tests were performed on the five groups of samples,it was found that the relative optimum annealing temperature was 470°C.After that,the specific contact resistance test of the sample under the annealing condition was carried out,and the test result was 2.21×10^-5Ω·cm².After that,the samples were tested by scanning electron microscope,transmission electron microscope,etc.The analysis of the two-dimensional element distribution mapping test results of the sample shows that O atoms diffuse into the Ti layer to oxidize it during the rapid thermal annealing process,and at the same time,oxygen vacancies are formed on the surface of theβ-Ga₂O₃ layer,and the existence of oxygen vacancies affects the electrons at the interface.The transport has a facilitating effect,which in turn forms an ohmic contact.Finally,X-ray photoelectron spectroscopy and electron energy loss spectroscopy were used to test the Ti layers before and after annealing.The test results showed that the Ti at the interface did not change before annealing and existed in elemental form;the Ti after annealing were basically Ti³⁺.2)Based on the first-principles calculation method of Density Functional Theory,a reasonable value ofβ-Ga₂O₃ cell band gap（4.87 e V）was obtained by MGGA+TB09functional to verify the accuracy of calculation.On this basis,different Ti（100）/β-Ga₂O₃（2?01）interface models were established,the structures of the different models were optimized,and the state density distribution and electrostatic potential difference of the optimized models were calculated.Finally,the electrical properties of the interface models were calculated and analyzed.According to the above results,the mechanism of ohmic contact between Ti andβ-Ga₂O₃ is explained.The results show that when Ti andβ-Ga₂O₃ contact directly,the interface appears schottky contact.When O atoms appear in the Ti layer,Ti reacts with O,and Ti is oxidized.In addition,due to the absence of O,a large number of oxygen vacancies are formed at the interface,reducing the barrier at the interface,which makes electron transport easier,leading to the formation of ohmic contact.The theoretical calculation results are consistent with the experimental results.In this paper,the formation mechanism of Ti/β-Ga₂O₃ ohmic contact is explored from the two aspects of experiment and theoretical calculation.The results show that after Au/Ti/β-Ga₂O₃ material is annealed at 470℃/120 s/N₂,Ti is oxidized to Ti³⁺,At the same time,the generation of oxygen vacancies at the interface is conducive to electron transport,thereby forming ohmic contacts.In addition,the oxidation degree of Ti will also affect the performance of ohmic contact,which needs further research and exploration.This study has guiding significance for the research and preparation of the physical mechanism ofβ-Ga₂O₃devices.