hi
have thermal velocities electron and hole in semiconductors constant?
What are they calculated?
thanks
Hello Ahmed,
the thermal velocity v can be estimated by
v = SQRT(3kT/m)
with k the Boltzmann constant and m the effective mass. Using this formulae, the velocity is proportional to the squareroot of the temperature. It is an approximation of classical statistical mechanics and valid only for nondegenerated semiconductors. You have a velocity distribution like in classical gases. The most particals (here electrons or holes) have a velocity near the average velocity.
Generally, the Fermi distribution must be considered. Furthermore, crystal properties like the mass anisotropy must be taken into account. But in many cases the upper expression gives a good estimation for the mean velocity.
Yours
R. Mitdank
Greetings.
See graphs of some dependencies for impurities in Fig. 1 and Fig. 2. For other SC materials there may be variations in values, but the trends of changes are approximately preserved.
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