i know effective mass of electron is higher than proton for si and Ge but why for GaAs its get opposite Reason??
Dear Naveed
The effective mass is defined as [reduced planck's const.]^2/the second derivative of enegy(E) w.r.t. wave vector(k)] i.e. it is a constant/curvature of the energy band. When the band (valence or conduction) curvature is large, we get low effective mass and vis versa. That is why changing material (Band structure) changes the effective mass values.
Best wishes
Dear Naveed,
I wonder how the effective mass of electron is greater than that of proton.
The effective mass of the electron is measured in units of its rest mass m0. For silicon and germanium the effective mass of electrons in the conduction band is smaller then the effective mass of holes.
In Ga As the effective mass of electrons is much smaller than that of holes.
The effective mass me is a quantum mechanical mass and as Mostafa said it is determined from the fitting of the conduction band minimum in energy band structure by a parabolic relation of the form (E- Ec )= P^2/2me,
where p is the electron momentum, Ec is the conduction band edge, and E is the electron energy.
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