Fabrication And Parameters Calculation Of β-Ga₂O₃ Schottky Barrier Diodes On Single Crystal Substrates And Epitaxial Films

Planar Schottky diodes with different electrode spacing were fabricated based on gallium oxide single crystal substrates and epitaxial films in this paper.A series of electrical tests were performed on the diodes,and the test results were analyzed.Furthermore,Schottky diode electrical parameters such as the ideal factor n,the height of the Schottky barrier ND,the carrier concentration of gallium oxide substrate ND,and the series resistance RS of the diode were calculated by using several methods based on I-V and C-V curve.The Ga₂O₃ crystal substrate grown by edged-defined film-fed grown method was tested by XRD,XPS,and SEM,and it was found that β-Ga₂O₃ single crystals exist other orientations besides the（100）crystal orientation.The Schottky diode based on the Ga₂O₃ crystal substrate has pbvious rectification characteristics,with a switching current ratio of 5×104 and on-state resistance of 51.4Ω·cm2.The device responds significantly to 254 nm UV light under reverse bias,with a light-dark current ratio of about 10 and a current ratio of only 1.05 under forward bias.The breakdown voltage is 52 V,and the breakdown field is 0.13 MV/cm.In addition,electrical parameters of Schottky diodes were systematically calculated using various methods,based on the I-V and C-V curves,and the results revealed that similar values were obtained by several methods.The ideal factor of the diode is 1.34-1.67,the series resistance is about 46 Ω·cm2,the Schottky barrier height is 0.86-1.04 eV,and the carrier concentration of Ga₂O₃ single crystal substrate is about 4.36×1017 cm-3.Through the analysis of diode performance by various parameters,it is concluded that the quality of the single crystal substrate is the main factor affecting the diode performance,and there are more defects inside the single crystal,and the diode is more prone to breakdown.Therefore,Schottky diodes with similar structure was fabricated on high-quality β-Ga₂O₃ epilayer grown by MOCVD.In addition,diodes with circular electrodes with sequentially increasing electrode spacing was fabricated to investigate the effect of electrode shape on device performance.Electrical tests were performed and it was found that the film-based diodes achieved better rectification with a switching current ratio of 1.5×106 and an on-state resistance of 2.0×104 Ω·cm2.The diodes showed better response for 254 nm UV light under both forward and reverse bias,with a forward photo and dark current ratio of 102 and under reverse bias,reaching 104.Similarly,the electrical parameters of the diode were calculated using various methods with ideal factors of 1.92-2.26,Schottky barrier heights of 0.62-1.14 eV,Ga₂O₃ epilayer carrier concentrations of 5.1 ×1016 cm-3,and series resistance of 2×104Ω·cm2.Comparing the performance of the Schottky diode based on crystal substrate and epilayer,it is found that the substrate quality is an important reason for the diode performance,and better performance can be achieved if the terminal structure is used to prevent premature breakdown.