Universality of the 1/3 shot-noise suppression factor in nondegenerate   diffusive conductors
  Shot-noise suppression is investigated in nondegenerate diffusive conductors by means of an ensemble Monte Carlo simulator. The universal 1/3 suppression value is obtained when transport occurs under elastic collision regime provided the following conditions are satisfied: (i) The applied voltage is much larger than the thermal value; (ii) the length of the device is much longer than both the elastic mean free path and the Debye length. By fully suppressing carrier-number fluctuations, long range Coulomb interaction is essential to obtain the 1/3 value in the low-frequency limit. 
T. Gonzalez, C. Gonzalez, J. Mateos, D. Pardo, L. Reggiani, O. M.   Bulashenko, J. M. Rubi