The near-band-edge photoluminescence at 80K
of heavily tellurium-doped degenerate liquid-phase-epitaxial gallium arsenide
layers (n=2*1018 cm-3) is investigated. The layers are compensated with shallow
germanium acceptors (the values of the degree of compensation are K=0.05-0.7)
during the epitaxial growth process. It is established that even at very low
concentration of shallow acceptors (K=0.05), the so-called mobile band appears
in the near-band-edge luminescence spectra. The peak energy of this band shifts
to lower energies, the non-equilibrium carrier generation rate decreases and
saturates at values E0T, which are considerably lower than those calculated for
the filling of the valence band density-of-states tails. It is assumed that
this discrepancy between theory and experiment is due to the uncertain
knowledge of the pre-exponential term in the expression for the
density-of-states tails and to the formation of some deeper fluctuation states
when there is a considerable difference between the concentrations of shallow
donors and acceptors. It is assumed that in this case some of these states act
as associates.
Source:IOPscience
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