Reduction of p/sup +/-n/sup +/ junction tunneling current for base current improvement in Si/SiGe/Si heterojunction bipolar transistors

The authors report a three-order-of-magnitude reduction in parasitic tunneling current at heavily doped p/sup +/-n/sup +/ Si/Si and SiGe/Si junctions grown by rapid thermal epitaxial chemical vapor deposition (CVD) compared with previously reported results in Si junctions fabricated by ion implantation. These results demonstrate the high quality of the epitaxial interface. The low tunneling currents allow higher limits to transistor base and emitter doping levels, yielding higher gains, reduced bias resistances, and higher Early voltages for scaled bipolar devices as well as Si/SiGe/Si heterojunction bipolar transistors.