I.R. absorption corresponding to transitions of holes from impurity levels to the valence band in silicon and germanium

Abstract

Absorption due to indirect transitions of holes from the boron levels to the valence band in silicon was recorded with the aid of penetrating exciting light. Two peaks for the absorption change produced by illumination were obtained which could be related to transitions from the two upper valence bands and from the lower valence band to the impurity level respectively. The participating phonon energies were determined and a value for the spin-orbit splitting in silicon was obtained. The measurements also made it possible to explain certain results from earlier measurements on borondoped and indium-doped silicon. The absorption increase recorded as a function of the exciting light intensity was in good agreement with a curve calculated theoretically for the assumed conditions. From the results obtained, the conclusion may be drawn that the time interval during which the bound holes preserve their k values is considerably larger than the lifetime of the holes. Finally, some measurements were made on intrinsic and gold-doped germanium and the spectral distribution of the absorption due to a gold level was determined.