What is effective mass in semiconductors?
Introduction. The effective mass of a semiconductor is obtained by fitting the actual E-k diagram around the conduction band minimum or the valence band maximum by a parabola. Most semiconductors can be described as having one band minimum at k = 0 as well as several equivalent anisotropic band minima at k ¹ 0.
What is effective mass and give its equation?
where ω is the angular frequency (2πν) and K is the propagation vector of the wave. This mass of an electron is called the effective mass of an electron, denoted as m*. The effective mass is thus determined by d 2E/dK 2.
What is effective mass formula?
The effective mass is determined by the band structure E(k). It can be calculated by mij-1= (2pi/h)2 d2E/d2kij. Furthermore, it can be measured by cyclotron resonanz.
What do you mean by effective mass of hole?
Effective mass is the mass of electrons or holes in the crystal to fit the Newton’s Law for them. We know, in crystals various forces act on electrons or holes. So the effective mass of electrons and holes come from including all these force.
What is positive effective mass?
A hole in a semiconductor thus moves with the opposite of the negative electron mass, i.e. as if it has a positive effective mass. Thus we seldom need concern ourselves with electrons having a negative effective mass. Instead we have holes with positive effective mass.
What is density of states effective mass?
However, the density of states effective mass m D * which governs the Seebeck coefficient is related to the single valley effective mass by m D * = N v 2/3m b *, where Nv is the valley degeneracy. This single valley mass is related to the diagonal elements of the mass tensor m 1,2,3 * by m b * = (m 1 *m 2 *m 3 *)1/3.
What is effective mass explain?
The effective mass is a quantity that is used to simplify band structures by modeling the behavior of a free particle with that mass. For some purposes and some materials, the effective mass can be considered to be a simple constant of a material.
What is called effective mass?
In solid state physics, a particle’s effective mass (often denoted. ) is the mass that it seems to have when responding to forces, or the mass that it seems to have when interacting with other identical particles in a thermal distribution.
What is positive and negative effective mass?
Is effective mass positive or negative?
As one can see from the dispersion curves, the effective mass of the electrons in the valence band, m*V, is always negative. (This means that a force in +x direction will cause such an electron to move in –x direction.)
Why is density of states important?
Distribution functions The density of states plays an important role in the kinetic theory of solids. The product of the density of states and the probability distribution function is the number of occupied states per unit volume at a given energy for a system in thermal equilibrium.
Is effective mass negative or positive?