The importance of neutral base recombination in compromising the gain of Si/SiGe heterojunction bipolar transistors

• Published in: IEEE transactions on electron devices Vol. 38; no. 8; pp. 1973 - 1976
• Main Authors: Shafi, Z.A., Gibbings, C.J., Ashburn, P., Post, I.R.C., Tuppen, C.G., Godfrey, D.J.
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.08.1991; Institute of Electrical and Electronics Engineers
• Subjects: Applied sciences; Bipolar transistors; Capacitance; Electronics; Exact sciences and technology; Flexible printed circuits; Germanium silicon alloys; Heterojunction bipolar transistors; Molecular beam epitaxial growth; Predictive models; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Silicon germanium; Switching circuits; Transistors; Voltage; Transistor base; Charge carrier recombination; Heterojunction transistor; Silicon; Manufacturing; Gain; Bipolar transistor; Electrical characteristic; Thin film
• ISSN: 0018-9383; 1557-9646
• DOI: 10.1109/16.119045

Si/SiGe heterojunction transistors were fabricated with 21.4 nm, heavily doped (5*10/sup 19/ cm/sup -3/) bases. Electrical results from these transistors are presented, and compared with results from comparable silicon homojunction control devices. These results indicate that the collector current is enhanced by a factor of 13, but the potential gain enhancement is compromised by a six-fold increase in base current. The base current is shown to be strongly dependent upon the collector/base voltage, indicating that recombination in the neutral base is the mechanism responsible for the increased base current. The recombination can only be modeled if the lifetime near the collector/base junction is significantly lower than elsewhere in the base. A simple two-region lifetime model predicts a value of 3.0*10/sup -13/ s close to the collector-base junction.< >