The Fabrication And Characterization Of Gallium Oxide Based Schottky Barrier Diode

Modern power electronics technology is the basic and core technology for the country to achieve carbon peak and carbon neutralization target,which is important to the sustainable development of human society.The fourth-generation semiconductor material gallium oxide（Ga₂O₃）has great potential in the field of modern power electronics and has attracted extensive attention because of its large bandgap and high theoretical breakdown electric field.It can use the economic melt method to produce single crystal substrates with large size and high quality.In recent years,gallium oxide based Schottky barrier diodes（SBD）,as an important fast diode power electronic device,has developed rapidly,but there is still the problem of relatively high reverse leakage current.Therefore,in this paper,the vertical Ga₂O₃ SBD is fabricated and characterized,and the fabrication method and structural design to improve the reverse leakage current of Ga₂O₃ SBD are explored.Firstly,a vertical Ga₂O₃ SBD is prepared.The electrical performance and thermal stability are analyzed by electrical characteristic measurement and electrical parameters extraction.The prepared SBD device has the high forward conduction current density（>900 A/cm²@4 V）,the low on-resistance（3.4mΩ.cm²）,and the low turn-on voltage（0.73 V）,which shows a good forward conduction characteristic.Subsequently,Ga₂O₃ SBD device is thermally annealed at 200-400℃for 5 min,respectively.The device after annealing shows the good forward conduction characteristics and the reduced reverse leakage,which shows good thermal stability of the Ga₂O₃ SBD.Then,in order to explore the process fabrication method and structural design to improve the reverse leakage of Ga₂O₃ SBD,the effects of oxygen plasma surface treatment,fluorine（F）plasma surface treatment and F treatment termination,selective F treatment and F treatment metal ring composite termination on the electrical characteristics of Ga₂O₃ SBD are studied in this paper.Specifically:（1）as for the effect of O₂ plasma surface treatment on the electrical properties of Ga₂O₃ SBD,the device with oxygen treatment has good forward characteristics,and the conduction current and on-resistance are basically consistent with those without oxygen treatment.The reverse leakage of the device with oxygen treatment is reduced.The barrier height extracted by the device with oxygen treatment is 1.23 e V,which is 0.13 e V higher than that without oxygen treatment.The results show that oxygen plasma treatment changes the interface properties of Schottky contact and modulates the barrier height.（2）As for the effect of F plasma surface treatment on the device,the reverse leakage is lower one order of magnitude than that of the device with basic structure.But the on-resistance is higher more than one order of magnitude than that of the device with basic structure.For the device with F plasma termination,the on-resistance is slightly greater than that of the basic device,but the reverse leakage is reduced.（3）As for the effect of the selective F treatment,the device with selective F treatment has good forward conduction characteristics and reduced reverse leakage.（4）As for the effect of F treatment metal ring composite termination on the device,the device with composite termination can effectively reduce the reverse leakage while maintaining good forward characteristics.The reverse leakage of the device with metal ring composite termination structure is less than 5×10^-6 A/cm² at-100 V,and the breakdown voltage is 171 V,26.6%higher than that of the basic device,which shows potential to improve reverse characteristics of device.In conclusion,the verticalβ-Ga₂O₃ SBD is prepared and characterized,and the process fabrication method and structural design to improve the reverse leakage are explored.Through the analysis of electrical characteristics,the results show that oxygen plasma surface treatment can modulate the barrier height and reduce the reverse leakage.Innovative F treatment metal ring composite termination structure can effectively reduce reverse leakage and increase reverse breakdown voltage.