Fabrication and Characterization of 4H-SiC P-N Junction Diodes by Selective-Epitaxial Growth Using TaC as the Mask

摘要

Selective nitrogen doping of 4H-SiC by epitaxial growth using TaC as the high-temperature mask has been demonstrated.Nomarski optical microscopy and scanning electron microscopy(SEM)were used to characterize selective growth of SiC.In addition,250-mum,square-shaped,p-n junction diodes by selective n-type epitaxial growth on a p-type epilayer were fabricated.The refilled fingers with different width were designed to vary the periphery/area(P/A)ratio.The effects of P/A ratio on the current-voltage(J-V)characteristics have been investigated.The ideality factor extracted from J-V characteristics is approx=2 at a temperature range of 25-275deg C,which indicates that the Shockley- Read-Hall recombination is the dominant mechanism in the conduction region.The reverse leakage current does not show dependence on P/A ratio for trench-refilled diodes.The room-temperature reverse leakage-current density at 100 V is less than 3.5 X 10~(-7)A/cm~2 for all diodes.Also,the reverse leakage current does not increase significantly with temperature up to 275deg C.The breakdown voltages measured at room temperature are about 450 V and 400 V for diodes without and with fingers,respectively.