摘要:
基于密度泛理论的第一性原理以及VASP软件,研究了电荷俘获存储器(CTM)中俘获层HfO2在不同缺陷下(3价氧空位(VO3)、4价氧空位(VO4)、铪空位(VHf)以及间隙掺杂氧原子(IO))对写速度的影响。对比计算了HfO2在不同缺陷下对电荷的俘获能、能带偏移值以及电荷俘获密度。计算结果表明： VO3, VO4与VHf为单性俘获, IO则是双性俘获, HfO2在VHf时俘获能最大,最有利于俘获电荷； VHf时能带偏移最小,电荷隧穿进入俘获层最容易,即隧穿时间最短；同时对电荷俘获密度进行对比,表明VHf对电荷的俘获密度最大,即电荷被俘获的概率最大。通过对CTM 的写操作分析以及计算结果可知, CTM俘获层m-HfO2在VHf时的写速度比其他缺陷时的写速度快。本文的研究将为提高CTM操作速度提供理论指导。
Abstract:
The programming speed of charge trapping memories (CTM) with different defects were studied based on the first principle and VASP package. The defects include threefold oxygen vacancy (VO3), fourfold oxygen vacancy (VO4), hafnium vacancy (VHf), and interstitial oxygen (IO). Trapping energy, energy band offset, and the trapping density were calculated and compared. Results show that VO3, VO4 only trap holes, VHf only trap electrons, and IO trap electrons and holes;the most important is the trapping energy which is greater in VHf. It is the best for trapping charges;because the charge tunneling into trapping layer is easy in VHf. It can also reduce the tunneling time. Finally, the trapping densities were compared with each other: VHf’s trapping density is greater than other defects, i.e. charges can be trapped easier than by other defects. All of these show that VHf is the best one for reducing programming time. This paper will provide a theoretical guidance for increasing the programming speed of CTM.
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