We only know the basic concepts of statistical distribution of semiconductors and carriers, we have to know the movement of carriers. So it is necessary to learn the carrier drift movement of the child.
The relationship between the conductivity and mobility: σ = nqμ
Carriers in the process of movement by the lattice thermal Zhendong or ionized impurity ions and other impurities influence, constantly being scattering, carrier velocity is changing the carrier scattering why suffer? The fundamental reason is because the periodic potential field is destroyed.
Scattering by ionized impurities: primarily a Coulomb potential field.
Scattering lattice vibrations: vibration number of different atoms are substantially in accordance with the winning combination fluctuation superposition principle, these fluctuations are known as basic lattice wave. Lattice wave vector q represents the wavelength and the lattice wave propagation direction. Q = 2pi / lamda.
N semiconductor crystal cell composed of the original, a total of N different wave vector q Gerber, a lattice wave each have six different lattice wave frequencies.
Other factors: the equivalent energy valley scattering, impurity scattering centers, dislocation scattering. Alloy scattering.
4.3 Relationship between the mobility of the impurity concentration and temperature
Gunn effect: voltage applied across the electrodes, when the semiconductor field exceeds 3 × 10 ^ 3, when the current to the semiconductor with a high frequency oscillation. Since electrons can be transferred from a valley to valley 2 can, inter-valley scattering, quasi greater momentum changes, greatly increasing the effective mass, the mobility is greatly reduced, the average drift velocity decreases, the conductivity decreased, resulting in negative resistance effect .
