An electrical method for measuring the difference bandgap across the neutral base in SiGe HBT's

This paper describes an electrical method for measuring the bandgap difference across the neutral base of SiGe heterojunction bipolar transistors (HBT's). It measures the effective bandgap difference due to differences in germanium concentration including the effects of heavy doping on bandgap reduction. Numerical device simulation was used to investigate the use of the proposed technique on high performance transistors with graded and uniform germanium profiles. Experimental verification of the technique is conducted on SiGe HBT devices fabricated using LPCVD.