On the assessment of few design proposals for 4H-SiC BJTs

A theoretical design analysis using two-dimensional numerical computer aided design tool (TCAD) is presented for 4H-SiC BJTs. Compared to conventional design, a high p-doped thin layer between the base–emitter region is effective to suppress the surface recombination between the base–emitter region. Using a surface recombination layer (SR layer of 60 nm thickness and acceptor doping of 1.0×1019 cm−3) between base–emitter region, a peak gain of 410 was obtained at 100 A/cm2. While a second epitaxy growth run is needed to utilize the advantage of this design, an alternate design with thin high doped (i.e., delta layer design) layer at the base–emitter junction is also interesting from the point of view of improving current gain with reduced on-resistance. A delta layer design thus produces a peak current gain of 300 at 100 A/cm2 and on-resistance value of 4 mΩ-cm2 at 300 K. Compared to the experimental data of 4H-SiC BJTs, present simulated analysis provides superior performance in terms of current gain.