Dissipative acceptor-valence-band tunnelling in GaAs:C_As

Abstract

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

Acoustic Phonon Activated and Assisted Tunnelling in Ge:Sb,P

“…Measurements were performed with the transient tunnelling spectrometer [5] which, for this purpose, was tuned to a special measuring regime [2,3]. Periodic and linearly ramped (993) voltage pulses were applied to the investigated samples in a form of mesas.…”

“…The second, phonon activated tunnelling mechanism [8], assumes that the electron at first is thermally excited to a higher-lying impurity level and only then tunnels through a more transparent donor barrier. To find the contribution of the phonon assisted tunnelling the acoustic deformation-potential interaction of the donor electron with the lattice vibrations was considered as in [2,3]. Figure 2 shows the ratio Rassis = W(T)/W(0) calculated with the parameter values which are typical of Ge:Sb.…”

“…The participation of acoustical phonons in the tunnelling process is expected to become important at low lattice temperatures and low barriers, of the order of, or smaller than, the optical phonon energy. Recently we have investigated the influence of acoustic phonons on the field ionization of phosphous atoms in a Si lattice [2] and of carbon atoms in a GaAs lattice [3].…”

Dissipative Tunnelling of Charge Carriers from Shallow Impurities

“…The experimental method is described in [6]. It uses the Transient Tunnelling Spectroscopy (TTS) and is based on the shift of the tunnelling peak on a time axis (or equivalently on a voltage axis), when the sample temperature is slowly scanned.…”

“…In the presented temperature range, thermal carriers in the conduction and valence bands were absent. A simple theory of field ionization of hydrogen-like impurities, which takes into account carrier interaction with acoustic phonons, will be used below [6].…”