DISSIPATIVE ACCEPTOR-VALENCE-BAND TUNNELING IN GAAS-C-AS

Field ionization properties of shallow carbon accepters in MBE GaAs, w here thermal lattice vibrations have an effect on the hole emission ra te, are presented. The excited energy levels of the carbon atom are re latively far from the ground level; therefore, it appeared possible to observe pure phonon-assisted tunnelling of a hole from a single (grou nd) level over a wide temperature range, from 4.2 K to 22 K. Experimen tal results are interpreted using a multiphonon field ionization model that takes into account the interaction of acoustic phonons with a lo calized centre via deformation and piezoelectric potentials. In the te mperature range considered, the influence of the deformation potential is found to predominate over the piezoelectric one.