Wave propagation modes in transferred electron devices: a phase-plane analysis

A simple phase-plane analysis of charge domain propagation is presented. It results from the continuity equation, where a waveform solution for the field is imposed. A field independent diffusion coefficient is considered. A piecewise linear approximation of the velocity field negative differential mobility relationship is used. Several propagation modes are thus predicted. For example, the experimentally well known bipolar and accumulation modes accompanied by field enhancement are found in transferred electron devices. Corresponding field impoverishment modes, which need to be experimentally confirmed, are nevertheless predicted. The modes might be possible with a hot electron initial condition all along the device, which could be achieved by a lateral heterojunction injection. Electrons falling into the lower valley would join the hot ones at the front, leaving behind a depleted zone. This could result in an impoverished electric field wave solution