Research on the origin of negative effect in uniform doping GaN-based Gunn diode under THz frequency

Abstract

The transport properties of GaN-based uniform doping Gunn diode are calculated by an ensemble Monte Carlo method. The drift velocity, electron density, and electric field distribution as a function of time in the device are illustrated under direct current (DC) and alternating current (AC) bias condition. With the help of port current, the relationship between electron transport status and port current can be acquired, which will be useful to understand the origin of negative differential resistance and guide the device design. Different from the traditional opinion, the maximum current do not appear at the same time when electron accumulation domain arrives at device anode. The reason is that when electron accumulation domain comes into heavily doped anode, the velocity will be decelerated a lot for highly ionized impurity scattering, and the electrons in the domain will be used to neutralize positive ion region which provides the electrons during formation of the domain. Some researchers believe that the electrons in the domain come from heavily doped cathode region, but our simulation shows clearly that the electrons come from heavily doped anode side. Finally, the AC simulation shows the possibility of negative differential resistance in GaN diode under THz frequency. What is more, AC simulation result has the same tendency with DC simulation.