Large-signal dynamic loss in gallium arsenide read avalanche diodes

In this paper we show that very large displacement currents may flow in high power Read diodes, especially when they are operated in the pulsed mode. These displacement currents may have peak amplitudes which are larger than the maximum possible conduction currents in the undepleted material. When this occurs, then the conduction current in the undepleted material must be augmented by a displacement current in that region. This displacement current is accompanied by a large field, in turn, causes abnormally large dissipation, since losses are proportional to the product of the conduction current in the undepleted material and the electric field. For practical diodes, this effect tends to limit the maximum modulation index to about 0.45. By special design of diodes, one may limit this anomalous loss, resulting in higher efficiency and higher power output.