Electrical determination of band-gap narrowing in bipolar transistors with Si and SiGe bases

The apparent band-gap narrowing in bipolar transistors with ion implanted and epitaxial Si0.83Ge0.17 bases was measured by a new method. The band-gap narrowing is only obtained by measuring the electric characteristics of the bipolar transistor at 300 K (ambient temperature) and 77 K (liquid nitrogen temperature) under the condition of known minority electron mobility, majority electron mobility and block resistance of the transistor. According to the temperature dependence on the collect current Ic (T), a graph of InIc as a function of VBE is plotted, based on the data extracted from the linear region of the Gummel plot when the temperature keeps constant. Two lines of InIc-VBE at 300 K and 77 K are obtained respectively. At the intersection of two lines, the values of band-gap narrowing in Si and Si0.83Ge0.17 bases are 41 meV and 125 meV respectively.EI04456-4592