Photoconductivity spectra for boron acceptors in Si1−xGex alloys

Far infrared photoconductivity spectra of B‐doped Si1−xGex grown by Czochralski technique have been investigated in the temperature region from 4.2 to 34 K as well as under high magnetic fields. The photo ionization transition from the ground state of boron acceptor to P3/2 valence band and that related to spin‐orbit splitting valence band (P1/2) are observed. The experimental results show that the ionization energy of boron acceptor in Si1−xGex decreases fast and linearly with the increase of Ge concentration for lower Ge composition, and 4% Ge contents make a decrease of 14 meV for the ionization energy of boron in Si0.96Ge0.04. The photoconductivity spectra hardly change with magnetic field up to 11 T.