On the Base Current Components in SOI Symmetric Lateral Bipolar Transistors

The base current components in semiconductor on insulator symmetric lateral bipolar transistors are examined in detail to yield insight into the underlying device physics. For Si-OI devices, the base current component due to recombination in the quasineutral base is negligible, the component due to injection into the emitter has a weaker than 1 NE dependence because of the effect of heavy doping. The component due to recombination in the emitter-base diode space-charge region is associated with the fabrication process, and could be reduced to a negligible level with process optimization. For SiGe-OI devices, the effect of heavy doping appears to be less than for Si-OI devices. The result is higher maximum current gain for SiGe-OI devices than for comparably doped Si-OI devices.