The drift velocity of electrons in silicon

is proportional to the electric field for all values of electric field

is independent of the electric field

increases at low values of electric field and decreases at high values of electric field exhibiting negative differential resistance

increases linearly with electric field and gradually saturates at higher values of electric field

The mobility of electrons in the conduction band for an intrinsic semiconductor will be

Greater than the mobility of holes in the valence band

Less than the mobility of holes in the valence band

Equal to the mobility of holes in the valence band

Motion of conduction electrons due to electric field E

Motion of conduction electrons due to random collisions

Collision of conduction electrons with each other

Repulsion to the conduction electrons due to inner electrons of ions

The dimensional formula of Mobility is given by,

[M^-1 L⁰ T²I¹]

Where,

Since, Drift velocity = Mobility × Electric Field

Therefore, Mobility (M) = Drift velocity × [Electric Field]^-1 . . . . (1)

The dimensional formula of drift velocity = [M⁰ L¹ T^-1] . . . . . (2)

Since, Electric Field = [Force × Charge^-1]

The dimensions of force and and charge = [M¹ L¹ T^-2] and [I¹T¹] respectively.

∴ The dimensional formula of Electric Field = [M¹ L¹ T^-2] × [I¹T¹]^-1 = [M¹ L¹ T^-3 I^-1] . . . (3)

On substituting equation (2) and (3) in equation (1) we get,

Mobility = Drift velocity × [Electric Field]^-1

Or, M = [M⁰ L¹ T^-1] × [M¹ L¹ T^-3 I^-1]^-1 = [M^-1 L⁰ T²I¹].

Therefore, mobility is dimensionally represented as [M^-1 L⁰ T²I¹].