Perimeter governed minority carrier lifetimes in 4H-SiC p+n diodes measured by reverse recovery switching transient analysis |
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Authors: | Philip G Neudeck |
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Affiliation: | (1) NASA Lewis Research Center, 21000 Brookpark Rd., M.S. 77-1, 44135 Cleveland, OH |
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Abstract: | Minority carrier lifetimes in epitaxial 4H-SiC p+n junction diodes were measured via an analysis of reverse recovery switching characteristics. Behavior of reverse recovery
storage time (ts) as a function of initial ON-state forward current (IF) and OFF-state reverse current (IR) followed well-documented trends which have been observed for decades in silicon p+n rectifiers. Average minority carrier (hole) lifetimes (τp) calculated from plots of ts vs IR/IF strongly decreased with decreasing device area. Bulk and perimeter components of average hole lifetimes were separated by
plotting 1/τp as a function of device perimeter-to-area ratio (P/A). This plot reveals that perimeter recombination is dominant in these
devices, whose areas are all less than 1 mm2. The bulk minority carrier (hole) lifetime extracted from the 1/τp vs P/A plot is approximately 0.7 μs, well above the 60 ns to 300 ns average lifetimes obtained when perimeter recombination
effects are ignored in the analysis. Given the fact that there has been little previous investigation of bipolar diode and
transistor performance as a function of perimeter-to-area ratio, this work raises the possibility that perimeter recombination
may be partly responsible for poor effective minority carrier lifetimes and limited performance obtained in many previous
SiC bipolar junction devices. |
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Keywords: | 4H-SiC minority carrier lifetime p-n junctions surface recombination |
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