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本文对Gunn 器件中掺杂梯度引起的静止畴进行计算机模拟.在器件的阳极端的掺杂存在一定的递增梯度的情况下,静止畴可能有两种产生方式:当扩散系数为常数时,畴在阴极形成,朝阳极渡越,最后静止于阳极,即渡越式的静止畴;当扩散系数与电场有某种一定的依赖关系时,畴可能在阳极成核、生长并静止于阳极,即非渡越式的静止畴.两者都导致一静态负阻特性,但电流波形不同. 从计算中归纳出掺杂梯度引起的静止畴的普遍特征:a)在靠近阳极一侧边缘处的扩散速度等于或大于漂移速度的二分之一,b)畴区内电子浓度分布趋于平坦. 计算中发现,当偏置电压高达一定值时,静止畴将转变为渡越畴.分析了这种转变的原因.并得出转变电压与均匀掺杂区的杂质浓度,阳极端的掺杂梯度及阴极端的凹口大小有关.
In this paper, we simulate the stationary domain caused by the doping gradient in the Gunn device.When there are some increasing gradients in the doping of the anode of the device, there are two possible ways to generate the stationary domain: when the diffusion coefficient is constant, When the diffusion coefficient and the electric field have some certain dependency, the domains may nucleate at the anode, grow and rest on the anode, that is to say, Non-transitory static domains, both of which lead to a static negative resistance characteristic but different current waveforms, general characteristics of quiescent domains caused by doping gradients are concluded from the calculations: a) diffusion near the anode-side edge The velocity is equal to or greater than one half of the drift velocity, and b) the distribution of electron concentration tends to be flat in the domain. It is found that when the bias voltage reaches a certain value, the quasi-stationary domain transforms into transition domain. The reason for the change is also shown that the transition voltage is related to the impurity concentration in the uniform doping region, the doping gradient at the anode end and the size of the notch at the cathode end.