Monte Carlo Analysis Of High-Field Transport Under Classical Size-Effect Conditions

When reducing the dimensions of a device, carrier transport goes from diffusive to ballistic regime and both current-voltage characteristics and Johnson-Nyquist noise caused by carrier scattering processes acquire new features. In diffusive regime the characteristic scattering processes are spatially isotropic, the current autocorrelation functions exhibit a standard exponential behavior and, therefore, the spectral densities of current fluctuations are Lorentzians. In ballistic regime the transport is mostly determined by transit times, which are either between the contacts or between the boundaries, and the associated scattering processes are spatially anisotropic depending on the sample geometry. In this regime, the current autocorrelation functions become non-exponential giving rise to: a redistribution of the noise at higher frequencies (blue-shift), a deviation of the noise spectrum from the Lor-entzian shape and, in particular cases, a series of geometrical resonances in the spectrum.1–5