SPATIAL VARIATION OF LOCAL CURRENT NOISE DUE TO IMPURITY SCATTERING AND LOCAL CHARGE-INDUCED NOISE

We analyze the noise characteristics associated with the fluctuation o f the number of electrons in two terminal elements. We find that the l ocal current noise on leads around a point contact varies spatially. T he local current noise resulting; from short wavelength fluctuations d iffers from the standard one resulting from long wavelength fluctuatio ns. The excess shot noise near the point contact decreases towards the leads, and the characteristic length is the mean free path of electro ns l. At distances longer than l from the contact, the local noise app roaches the pure thermal noise given by 4k(B)TG(Q) with the quantized conductance G(Q). We also find that the tunneling current of resonant tunneling devices (RTDs) is strongly influenced by the existence of th e immobile charges captured by the localized traps. By treating the el ectron capture and emission processes kinematically, we simulate rando m telegraph noise (RTN).