Effect of velocity/field characteristics on the operation of avalanche-diode oscillators

The velocity/field characteristics of the carriers traversing the drift region in an avalanche diode can have profound effects on the operational parameters of the device. The letter describes these effects in terms of a theory that imposes the velocity/field characteristic on the simple Read-diode model. The effect of the velocity/field dependence is to alter the external induced current waveshape at large signal levels. For carriers with characteristics similar to electrons in GaAs, the modification is in the form of a spike in a class-C configuration. In silicon, the spike is negative and lossy. The analysis demonstrates one of the basic advantages of GaAs as a material for avalanche-diode fabrication and also predicts a power-saturation effect in silicon Read diodes at efficiencies in the 20 to 25% region.