A Study of the Transformations between Stationary and Transit Domains in a Gunn Device
Gunn器件中畴的静止-渡越-静止模式的实验观察和计算机模拟

The transformations between stationary and transit domains in a Gunn device whichhas a n~ -n-n~ sandwich structure with a doping gradient near the anode are investigated.Experimental observation and computer simulation are carried out.When the domainreaches the anode,it will stop and become a quasi-stationary domain.By this time thefield outside the domain reaches its maximum value.If the bias voltage is not highenough so that this maximum value of field outside the domain does not cause a newdomain to be created at the notch near the cathod, the quasi-stationary domain willthen readjust itself to become a real stationary domain,while the field outside the do-main will decrease to a fixed value,which is independent of the bias voltage.Theoret-ical analysis has been carried out and an analytical relationship between the field out-side the domain for real stationary domains and the doping density in the active regionof the device is obtained.If the bias voltage increases,the maximum value of the fieldoutside the domain,which is accompanied by the quasi-stationary domain,increases too.As soon as this maximum value becomes high enough to cause a new domain to be createdat the notch,the stationary domain mode will transform into transit domain mode.Itis noticed that the maximum value of the field outside the domain depends not only onthe instantaneous value but also on the increasing rate of the bias voltage.If the biasvoltage increases further,the rear part of the quasi-stationary domain will extend overthe notch near the cathode, and a new stationary domain will occur again.This state willbe maintained until the avalanche takes place.The influence of diffusion coefficient onstationary domain and the temperature dependence of the threshold voltages of the twokinds of transformation between stationary and transit domains are also discussed.