Strained Axial Si/Ge Heteronanowire Devices: From Tunneling Transistors to Optical Sources

我们计划与T。皮克罗在洛斯阿拉莫斯的外延组。 先前的工作已经表明，侧壁应变弛豫极大地扩展了可用的带隙和应变工程，允许将基本上任意SiGe成分的片段并入轴向纳米线中。 我们计划研究以下几类器件：i）轴向Si/Ge异质纳米线隧穿晶体管，由于沿着纳米线的带隙和应变工程与栅极全包围器件几何结构相结合，其有望实现更尖锐的开关与更高的隧穿电流的组合; ii）具有高导带和价带势垒的Si/Ge双势垒隧穿结构，其通过放宽窄异质纳米线中的临界厚度限制而成为可能; iii）具有横向尺寸限制的Si/Ge/Si pn异质结，由于Ge区域中更窄的伪直接带隙，有望实现更强的光学跃迁。实验结果将与连续弹性和分子动力学的数值能带结构模拟进行比较。（同样，与Picraux组合作）。更广泛的影响具有栅极全包围几何形状的异质纳米线隧穿晶体管包括与硅技术兼容的低压开关的更现实的候选者之一。 此外，我们的工作将提供实验数据的原子模拟的非均匀应变在~10 nm的长度尺度。洛斯阿拉莫斯合作研究将增加研究生教育的影响，由于延长学生访问洛斯阿拉莫斯。 本科生将在分部工作，包括来自少数民族机构的REU学生（通过布朗MRSEC确定）。

INTELLECTUAL MERITWe propose to study devices fabricated from sub-50 nm diameter nanowires with axial Si/Ge heterojunctions grown by the vapor-liquid-solid technique in collaboration with T. Picraux's epitaxy group at Los Alamos. Previous work has shown that sidewall strain relaxation greatly expands the available bandgap and strain engineering, allowing segments of essentially arbitrary SiGe composition to be incorporated into the axial nanowire. We plan to study the following classes of devices:i) axial Si/Ge heteronanowire tunneling transistors, which promise a combination of sharper switching together with higher tunneling currents due to bandgap and strain engineering along the nanowire combined with the gate-all-around device geometry; ii) Si/Ge double-barrier tunneling structures with high conduction and valence band barriers made possible by the relaxation of critical thickness limits in narrow heteronanowires;iii) Si/Ge/Si pn heterojunctions with lateral size confinement that promise stronger optical transitions due to narrower and pseudo-direct bandgap in the Ge region.Experimental results will be compared to numerical band structure simulations from both continuum elasticity and molecular dynamics (again, in collaboration with the Picraux group).BROADER IMPACTHeteronanowire tunneling transistors with gate-all-around geometry comprise one of the more realistic candidates for low-voltage switching compatible with silicon technology. Also, our work will provide experimental data for atomistic simulations of inhomogeneous strain at ~10 nm length scale. The Los Alamos collaboration research will have added graduate education impact due to extended student visits to Los Alamos. Undergraduates will work on sub-sections, including REU students from minority institutions (identified through the Brown MRSEC).