The role of nitrogen doping in ALD Ta2O5 and its influence on multilevel cell switching in RRAM
The role of nitrogen doping in ALD Ta2O5 and its influence on multilevel cell switching in RRAM
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DOI：
10.1063/1.4978033
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发表时间：
2017-03-06
影响因子：
4
通讯作者：
Chalker, P. R.
中科院分区：
文献类型：
--
作者：
Sedghi, N.;Li, H.;Chalker, P. R.
阐述了氮掺杂对原子层沉积的N掺杂Ta2O5的阻态转换稳定性和记忆窗口的作用。氮掺入增加了电阻存储状态的稳定性，这归因于与氧空位相关的电子缺陷能级的中和。屏蔽交换混合泛函近似的密度泛函模拟表明，在氧化物网络中的氮掺杂剂原子的掺入去除了O空位midgap缺陷态，从而抵消多余的缺陷，消除替代导电路径。通过N掺杂有效降低空位诱导缺陷态的密度，演示了3位多级单元切换，由八个不同的阻性存储器状态组成，通过控制重置期间的设置电流合规性或最大电压来实现。氮掺杂具有三重效果：拓宽开关存储器窗口以容纳更多的中间状态，提高状态的稳定性，以及在复位期间为多级单元开关提供逐渐复位。N掺杂的Ta2O5器件具有相对小的置位和复位电压（<1V），并且由于掺杂而具有减小的可变性。
The role of nitrogen doping on the stability and memory window of resistive state switching in N-doped Ta2O5 deposited by atomic layer deposition is elucidated. Nitrogen incorporation increases the stability of resistive memory states which is attributed to neutralization of electronic defect levels associated with oxygen vacancies. The density functional simulations with the screened exchange hybrid functional approximation show that the incorporation of nitrogen dopant atoms in the oxide network removes the O vacancy midgap defect states, thus nullifying excess defects and eliminating alternative conductive paths. By effectively reducing the density of vacancy-induced defect states through N doping, 3-bit multilevel cell switching is demonstrated, consisting of eight distinctive resistive memory states achieved by either controlling the set current compliance or the maximum voltage during reset. Nitrogen doping has a threefold effect: widening the switching memory window to accommodate the more intermediate states, improving the stability of states, and providing a gradual reset for multi-level cell switching during reset. The N-doped Ta2O5 devices have relatively small set and reset voltages (< 1 V) with reduced variability due to doping.