Advanced Device Technologies, Sandia National Laboratories, Albuquerque, NM 87185, USA.
Nanotechnology. 2011 Jun 3;22(22):225202. doi: 10.1088/0957-4484/22/22/225202. Epub 2011 Apr 1.
A singly ionized two-donor molecule in silicon is an interesting test-bed system for implementing a quantum bit using charge degrees of freedom at the atomic limit of device fabrication. The operating principles of such a device are based on wavefunction symmetries defined by charge localizations and energy gaps in the spectrum. The Stark-shifted electronic structure of a two-donor phosphorus molecule is investigated using a multi-million-atom tight-binding framework. The effects of surface (S) and barrier (B) gates are analyzed for various voltage regimes. It is found that gate control is smooth for any donor separation, although at certain donor orientations the S and B gates may alter in functionality. Effects such as interface ionization, saturation of the lowest energy gap, and sensitivity to donor and gate placements are also investigated. Excited molecular states of P(2) + are found to impose limits on the allowed donor separations and operating gate voltages for coherent operation. This work therefore outlines and analyzes the various issues that are of importance in the design and control of such donor molecular systems.
硅中的单电离双施主分子是一个有趣的测试平台系统，可用于在器件制造的原子极限内使用电荷自由度实现量子位。这种器件的工作原理基于电荷局域化和能带隙定义的波函数对称性。使用数百万原子紧束缚框架研究了双磷施主分子的斯塔克位移电子结构。分析了不同电压区域的表面（S）和势垒（B）门的影响。结果发现，对于任何施主间隔，门控都是平滑的，尽管在某些施主取向下，S 和 B 门的功能可能会发生变化。还研究了界面电离、最低能隙饱和以及对施主和门位置的敏感性等效应。发现 P(2) + 的激发分子态对相干操作中允许的施主间隔和工作门电压施加了限制。因此，这项工作概述和分析了在这种施主分子系统的设计和控制中非常重要的各种问题。
