Anode domain transient processes in supercritical Gunn diodes

Using a computer Gunn-diode model the transient processes connected with a supercritical anode domain are investigated. Anode domain formation, domain response to step-bias variation and anode domain annihilation are studied. It is shown, that transient processes in a diode with an anode domain are characterized by considerable larger times, than in a diode with a travelling (Gunn) domain with the same sample length, carrier concentration and bias voltage. Anode formation and transformation can be described as a process of nonlinear domain capacitance C_d charging via a nonlinear resistance R_d which is determined by the field outside the domain. Simple stationary equations can be used to find all parameters of these transient processes. In some practically important cases the anode domain transformation process can be described analytically. It is also shown that anode domain annihilation is characterized by a strong dependence of the annihilation time on the bias. The annihilation time increases indefinitely with the increasing bias up to the sustaining threshold.