Frequency Conversion in Punch-Through Semiconductor Devices.

摘要

The objectives of this investigation are to study the frequency conversion properties of punch-through semiconductor devices and to establish the frequency regions of their potential application as efficient detectors and mixers of information-bearing signals. The physics of two punch-through devices are studied in detail: the three-terminal punch-through transistor and the two-terminal BARITT (barrier injection transit-time) diode. The particle current injection process for both devices is examined and identified as simple diffusion over a potential barrier (exponential injection with respect to the barrier height). Dc and small-signal ac models for both punch-through structure are derived from standard bipolar junction transistor theory by applying a current-dependent, rather than the standard voltage-dependent, boundary condition for the minority carrier concentration at the collector edge of the low-field base region. The small-signal models include carrier transit-time effects in the diffusion-drift, reverse-biased regions of the devices by means of a transit-time factor similar to the factor used in the standard frequency domain analysis of pure saturated drift transit-time diodes. The small-signal noise properties of the BARITT diode are developed employing the same techniques used in the formulation of the BARITT diode circuit model. Both, small-signal impedances predicted by the circuit model and small-signal noise measures predicted by the noise analysis, compare very well with experimentally measured values of typical BARITT structures.