Monte Carlo calculation of noise transport in a two-dimensional diode

The noise transport phenomena in a two-dimensional diode operated under space-charge-limited conditions are investigated by means of the statistical Monte Carlo method. Effects on the transport characteristics of an electron beam by the multi-dimensional nature of the potential distribution in the vicinity of the potential minimum are evaluated. Contrary to both the single velocity and multivelocity linear small-signal noise theories, the noise parameters
S
, II,
S
-- II and
S
+ II are found to be nonconservative. A reduction in the equivalent noise figure from 6.96 db corresponding to full-shot noise input at the cathode to approximately 2 db is observed at the anode of the two-dimensional diode for a wide range of frequencies. A substantial amount of correlation between the kinetic potential and the current fluctuations is developed in the multivelocity region beyond the potential minimum. It is believed that the improvement in noise performance of the two-dimensional diode over the one-dimensional model is directly attributable to the space-charge potential-depression effects by which an additional amount of velocity spread is introduced in the electron beam, creating an extension of the multivelocity non-linear region. The theoretical minimum-noise figures obtained indicate that possibly two-dimensional dc effects are more important than two-dimensional ac effects in essentially hollow-beam low-noise devices.