The first principal degradation mechanism of the low field mobility is phonon scattering in the lattice.
The temperature dependence is modeled according to a simple power law:
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Following Table 3.1 different mobilities are applied of the lowest valley at different material compositions. This allows for more precise modeling, as shown for the ternary compound semiconductors in Fig. 3.3, Fig. 3.4, and Fig. 3.5.
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For the low field mobility of GaN a distinction is made
for the growth by MBE and MOCVD, see [81]. The temperature
coefficient is extracted from experimental data given by Look et
al. in [164] and by MC simulations by Bhapkar et al. in
[38]. For AlN the mobility is given as determined by MC
simulations by Anwar et al. in [17]. For InN there is a
tremendous discrepancy between various simulation predictions and
the experimental values obtained. This is due to the high
unintentional doping concentrations of about 10
cm
still prevailing in the experimental samples [246].
The second dominant effect degrading the transport properties is scattering due to ionized impurities (I). For binary semiconductors the following model is well established to model the dependence [62]: