Direct Band Gap Narrowing In Highly Doped Ge

Direct band gap narrowing in highly doped n-type Ge is observed through photoluminescence measurements by determining the spectrum peak shift. A linear relationship between the direct band gap emission and carrier concentration is observed. We propose a first order phenomenological model for band gap narrowing based on two parameters whose values for Ge are E-BGN = 0.013 eV and Delta(BGN) = 10(-21) eV/cm(-3). The application of these results to non-invasive determination of the active carrier concentration in submicron areas in n-type Ge structures is demonstrated. (C) 2013 AIP Publishing LLC [http://dx.doi.org/10.1063/1.4802199]