Quantum thermal noise of hot-electron transport in semiconductors under a strong electric field

Quantum thermal noise of hot-electron transport in homogeneous semiconductors under a uniform and strong electric field is studied. Based on the separation of the center-of-mass motion from the relative motions of electrons in a semiconductor with a parabolic electron band, a Langevin-type equation for the center-of-mass motion is obtained. A generalized fluctuation-dissipation relation is derived for the symmetrized force-force correlation function. In terms of this relation and a memory function, all the noise quantities, the spectra of voltage and current fluctuation and the diffusion coefficients, can be derived in a natural way. The expressions of these noise quantities will reduce to the corresponding well-known formulas, the Nyquist and Einstein relations, in the zero-field limit. [...]