In semiconductors the velocity of carriers gets saturated after a certain value of electric field. In silicon it occurs at around $10^4 kV/cm$ and in GaAs at some other value.
- What factors are involved here?
- Is it related to the value of band-gap alone or other parameters are at play?
Furthermore, suppose the value of saturated velocity of an electron in Si at room temperature is $10^7 cm/s$, for an electron in GaAs it is even higher.
- Why is that so?
Best Answer
Maybe this will be helpful: Ridley–Watkins–Hilsum theory. It somehow explains why velocity of electron saturate. High speed electrons can change valley in band structure and gain higher mass, less mobility. Similar to scattering by optic phonon.