8.3 Low-Field Transport
233
(a)
(b)
Fig. 8.6 Temperature dependence of the electron mobility in n-type a bulk ZnO and b a PLD-grown ZnO thin film on
sapphire. In the latter, grain-boundary scattering is limiting the mobility. Squares are experimental data, solid lines are
theoretical mobilities for various scattering mechanisms and combined mobility according to (8.12). Experimental data
from [737]
Fig. 8.7 Calculated
temperature dependence of
the electron mobility in
n-type Al 0.25 Ga 0.75 N,
(N D = 5 × 10 17 cm −3 ).
PO: polar optic scattering,
PE: piezoelectric
scattering, ADP: acoustic
deformation potential
scattering. Adapted
from [592]
Since the carrier concentration increases with increasing temperature and the mobility decreases,
the conductivity has a maximum, typically around 70 K (see Fig. 8.8). At very high temperature, when
intrinsic conduction starts, σ shows a strong increase due to the increase in n.
At low temperature, the disorder due to doping (random positions of the impurity atoms) leads to a
temperature driven metal–insulator transition as depicted in Fig. 8.21.
8.3.12 Doping Dependence
The mobility decreases with increasing dopant concentration as already shown in Figs. 8.3 and 8.5a. In
Fig. 8.9a the low doping limit is due to deformation potential scattering; the decrease with doping is due
233
(a)
(b)
Fig. 8.6 Temperature dependence of the electron mobility in n-type a bulk ZnO and b a PLD-grown ZnO thin film on
sapphire. In the latter, grain-boundary scattering is limiting the mobility. Squares are experimental data, solid lines are
theoretical mobilities for various scattering mechanisms and combined mobility according to (8.12). Experimental data
from [737]
Fig. 8.7 Calculated
temperature dependence of
the electron mobility in
n-type Al 0.25 Ga 0.75 N,
(N D = 5 × 10 17 cm −3 ).
PO: polar optic scattering,
PE: piezoelectric
scattering, ADP: acoustic
deformation potential
scattering. Adapted
from [592]
Since the carrier concentration increases with increasing temperature and the mobility decreases,
the conductivity has a maximum, typically around 70 K (see Fig. 8.8). At very high temperature, when
intrinsic conduction starts, σ shows a strong increase due to the increase in n.
At low temperature, the disorder due to doping (random positions of the impurity atoms) leads to a
temperature driven metal–insulator transition as depicted in Fig. 8.21.
8.3.12 Doping Dependence
The mobility decreases with increasing dopant concentration as already shown in Figs. 8.3 and 8.5a. In
Fig. 8.9a the low doping limit is due to deformation potential scattering; the decrease with doping is due