HEAVILY DOPED SILICON STUDIED BY LUMINESCENCE AND SELECTIVE ABSORPTION.

Low temperature photoluminescence and selective absorption (photoluminescence excitation spectroscopy) measurements are used to study heavily doped n- and p-type silicon. From the selective absorption spectra, an accurate determination of the optical band gap up to charge carrier concentrations of 1. 5 multiplied by 10**1**9 cm** minus **3 was performed. For carrier concentrations in the range of 10**1**7-10**1**8 cm** minus **3 impurity-induced no-phonon band-to-band absorption was observed in addition to the normal phonon assisted indirect interband absorption. In the emission spectra an increase of the no-phonon and of the TA-phonon assisted recombination, compared to the TO-phonon assisted emission, was found for carrier concentrations above 2 multiplied by 10**1**9 cm** minus **3. This indicates an impurity induced change in the transition matrix elements.