Determination of the spin-orbit splitting in the valence band of silicon by means of infra-red absorption

Abstract

Absorption measurements were made on intrinsic as well as on boron- and indium-doped silicon in the wavelength interval 1–35 μm and with temperatures between 30°K and 330°K. The measurements were performed by a method in which free carriers were excited by light with photon-energy greater than the fundamental band gap, and the resulting absorption change was recorded. (5,10) Three independent determinations of the spin-orbit splitting in the valence band were made. The method made it possible to eliminate the inter- and intra-band absorption and record the absorption due to transitions from impurity levels to the valence band. In boron- and indium-doped crystals an absorption band due to transitions from the impurity levels to the υ3-band was detected from which a determination of the spin-orbit splitting could be made. From the boron-doped samples the value 0.037 eV was obtained for the spin-orbit splitting at 88°K. The value 0.0383 eV was obtained for the spin-orbit splitting at 30°K and 88°K from the absorption band due to transitions from the υ1- to the υ3-band, when the interband absorption in an intrinsic sample was recorded. From this band a determination of the effective hole mass in the split-off band could be made, and at 88°K the value 0⋯42 m 0 was obtained.