6.5.2
Figure 6.8: Visualization of (a) the direction of carrier fluxes due to an electric field; and (b) the corresponding band
diagram.
The electron and hole drift current densities are then given as
Combining Eqs. (6.24a) and (6.24b) leads to the total drift current,
Mobility is a measure of how easily the charge particles can move through a
semiconductor material. For example, for c-Si with a doping concentration N D or N A at 300
K, the mobilities are
µ n ≈ 1 360 cm
2
V
−1
s
−1
,
µ p ≈ 450 cm
2
V
−1
s
−1 ,
respectively. As mentioned earlier, the motion of charged carriers is frequently disturbed
by collisions. When the number of collisions increases, the mobility decreases. Increasing
the temperature increases the collision rate of charged carriers with the vibrating lattice
atoms, which results in a lower mobility. Increasing the doping concentration of donors or
acceptors leads to more frequent collisions with the ionized dopant atoms, which also
results in a lower mobility. The dependence of mobility on doping and temperature is
discussed in more detail in standard textbooks for [24, 31].
Diffusion
Diffusion is a process whereby particles tend to spread out from regions of high particle
concentration into regions of low particle concentration as a result of random thermal
motion. The driving force of diffusion is a gradient in the particle concentration. In
contrast to the drift transport mechanism, the particles need not be charged to be involved
Figure 6.8: Visualization of (a) the direction of carrier fluxes due to an electric field; and (b) the corresponding band
diagram.
The electron and hole drift current densities are then given as
Combining Eqs. (6.24a) and (6.24b) leads to the total drift current,
Mobility is a measure of how easily the charge particles can move through a
semiconductor material. For example, for c-Si with a doping concentration N D or N A at 300
K, the mobilities are
µ n ≈ 1 360 cm
2
V
−1
s
−1
,
µ p ≈ 450 cm
2
V
−1
s
−1 ,
respectively. As mentioned earlier, the motion of charged carriers is frequently disturbed
by collisions. When the number of collisions increases, the mobility decreases. Increasing
the temperature increases the collision rate of charged carriers with the vibrating lattice
atoms, which results in a lower mobility. Increasing the doping concentration of donors or
acceptors leads to more frequent collisions with the ionized dopant atoms, which also
results in a lower mobility. The dependence of mobility on doping and temperature is
discussed in more detail in standard textbooks for [24, 31].
Diffusion
Diffusion is a process whereby particles tend to spread out from regions of high particle
concentration into regions of low particle concentration as a result of random thermal
motion. The driving force of diffusion is a gradient in the particle concentration. In
contrast to the drift transport mechanism, the particles need not be charged to be involved