Small-signal design theory and experiment for the punch-through injection transit-time oscillator

Abstract

The small-signal theory of the punch-through ‘barrier-injection and transit-time’ (BARITT) diode is given and the physical mechanisms of device operation are described. Both velocity modulation and charge density modulation components of current are included and the effects of carrier diffusion in the source regions of the device are taken into account by using an equivalent small-signal conductivity for the potential barrier which controls charge injection. It is shown how carrier bunching in the source regions creates space-charge waves which propagate through the source-drain space and generate power as the associated component of current moves into anti-phase with the local electric field. Theoretical curves are presented for a typical PNP silicon device and agree well with experimental measurements of series resistance and series capacitance. A device of area 1·25 × 10 −8 m 2 (5 thou. diameter) and source to drain spacing of 5 μm made in 5 Ω cm material was found to possess negative resistance over the wide frequency range from about 5 GHz to about 12 GHz with a maximum value of about — 5 Ω.