display | more...

See also conductivity

Newton's second law says that F = ma, where F is the force on a particle, m is its mass, and a is its acceleration. When a charged particle is in a solid material in which an electric field is applied, the particle feels the force qE from the electric field (more generally an external force Fext ) and a force Fint from the nucleii and other particles in the solid. Luckily, if a solid is a crystal, the effect of the internal forces can be lumped into a new effective mass m*, and Fext = m*a. This is a nice concept since it eases analysis of the dynamics of electron and hole carrier transport in crystals.

It can be shown that m* = h2(d2E/dk2)-1, where E(k) vs. k is the energy vs. Bloch wavevector relationship of the energy band in which a carrier resides. For a free particle, E = h2k2/2m, so m* = m, as expected.

h is really "hbar," or Planck's constant over 2π.

Effective masses of electrons and holes (respectively) in semiconductors (in units of m*/mo where mo is the rest mass of an electron).

It is interesting to note that the effective masses of electrons in crystals are all smaller than the free electron masses.

Log in or register to write something here or to contact authors.