Patent attributes
A bipolar transistor which has a base formed of a combination of shallow and deep acceptors species. Specifically, elements such as Indium, Tellurium, and Gallium are deep acceptors in silicon, and are appropriate for such an application, in combination with boron as the shallow acceptor. The use of a deep acceptor for doping the base of the transistor has the benefit of providing a doping species, which increases in ionization as the temperature rises. At elevated temperatures, the fraction of, for example, indium which is ionized increases and it results in an increased Gummel number, driving down the current gain. In other words, the enhancement of the Gummel number between room temperature and an elevated temperature compensates for the increase in the ratio of collector and base currents due to band gap narrowing effects. Thus, a zero temperature coefficient bipolar transistor is provided.
