Properties of Homoepitaxial 4H-SiC and Characteristics of Ti/4H-SiC Schottky Barrier Diodes

摘要

This paper describes the properties of the homoepitaxial 4H-SiC layer, the fabrication and electrical parameters of Ti/4H-SiC Schottky barrier diode (SBD). The 4H-SiC epitaxial layers, grown on the commercially available 8°off-oriented Si-face(0001) single-crystal 4H-SiC wafers, have been performed at 1550～1600℃ by using the step controlled epitaxy with low pressure chemical vapor deposition. X-ray diffraction measurement result indicates the single crystal nature of the epilayer, and Raman spectrum shows the typical 4H-SiC feature peaks. When the off-oriented angle of substrate is 8°, the epitaxial growth perfectly replicates the substrate's polytype. High quality 4H-SiC epilayer has been generated on the 4H-SiC substrate. Ti/4H-SiC SBDs with blocking voltage 1kV have been made on an undoped epilayer with 12um in thick and 3×10~(15)cm~(-3) in carrier density. The ideality factor n=1.16 and the effective barrier height φ_e=0.9V of the Ti/4H-SiC SBDs are measured with method of forward density-voltage (J-V). The diode rectification ratio of forward to reverse (defined at ±1V) is over 10~7 at room temperature. By using B~+ implantation, an amorphous layer as the edge termination is formed. The SBDs have on-state current density of 200A/cm～2 at a forward voltage drop of about 2V. The specific on-resistance for the rectifier is found to be as 6.6mΩ·cm～2.