290
9 Optical Properties
Fig. 9.37 Photocurrent
spectrum of Si:Mg.
Transitions are due to Mg
+
i
from its 1s state to excited
states as labeled and
indicated by vertical lines.
CB denotes the conduction
band edge (ionization
limit). Above the CB edge
(shaded area)
phonon-assisted absorption
occurs (Fano resonances).
For comparison the
absorption spectrum below
CB is shown shifted by the
phonon energy (dashed
line). Above the plot, the
transition mechanisms
(photothermal ionization
and Fano resonance) are
schematically shown.
Adapted from [907]
2
1
0.8
0.6
0.4
1
2
3
4
i
i
-17
2
GaAs
Au
Mn
Cu
Ag
Fig. 9.38 Absorption spectra (σ = α/ p) due to various deep impurities in GaAs as labeled. The dashed line is a
theoretical lineshape assuming a hole bound to a δ-potential. The energy axis is scaled by the ionization energy. The
kink for Mn at 3.5 E i ≈ 450 meV is due to the onset of absorption into the split-off valence band. Adapted from [314]