University of Grenoble Alpes, LTM , F-38000 Grenoble, France.
Nano Lett. 2014 Sep 10;14(9):5140-7. doi: 10.1021/nl5019707. Epub 2014 Aug 19.
As MOSFETs are scaled down, power dissipation remains the most challenging bottleneck for nanoelectronic devices. To circumvent this challenge, alternative devices such as tunnel field effect transistors are potential candidates, where the carriers are injected by a much less energetically costly quantum band to band tunneling mechanism. In this context, axial nanowire heterointerfaces with well-controlled interfacial abruptness offer an ideal structure. We demonstrate here the effect of tuning the Ge concentration in a Si1-xGex part of the nanowire on the Si/Si1-xGex and Si1-xGex/Si interfacial abruptness in axial Si-Si1-xGex nanowire heterostructures grown by the Au-catalyzed vapor-liquid-solid method. The two heterointerfaces are always asymmetric irrespective of the Ge concentration or nanowire diameter. For a fixed diameter, the value of interface abruptness decreases with increasing the Ge content for the Si/Si1-xGex interface but shows no strong Ge dependence at the Si1-xGex/Si interface where it features a linear correlation with the nanowire diameter. To rationalize these findings, a kinetic model for the layer-by-layer growth of nanowire heterostructures from a ternary Au-Ge-Si alloy is established that predicts a discrepancy in Ge concentration in the layer and the catalyst droplet. The Ge concentration in each layer is predicted to be dependent on the composition of the preceding layer. The most abrupt heterointerface (∼5 nm) is achieved by growing Si1-xGex with x = 0.85 on Si in a 25 nm diameter nanowire.
随着 MOSFET 的缩小，功耗仍然是纳米电子器件最具挑战性的瓶颈。为了克服这一挑战，替代器件，如隧道场效应晶体管，是潜在的候选者，其中载流子通过能量成本低得多的量子带对带隧道机制注入。在这种情况下，具有良好控制界面陡峭度的轴向纳米线异质结提供了理想的结构。我们在这里展示了在通过 Au 催化的汽-液-固法生长的轴向 Si-Si1-xGex 纳米线异质结构中，通过调整纳米线中 Si1-xGex 部分的 Ge 浓度，对 Si/Si1-xGex 和 Si1-xGex/Si 界面陡峭度的影响。无论 Ge 浓度或纳米线直径如何，两个异质界面总是不对称的。对于固定直径，Si/Si1-xGex 界面的界面陡峭度随 Ge 含量的增加而减小，但在 Si1-xGex/Si 界面上没有强烈的 Ge 依赖性，在该界面上，它与纳米线直径呈线性相关。为了解释这些发现，建立了一个从三元 Au-Ge-Si 合金生长纳米线异质结构的层状生长的动力学模型，该模型预测了层和催化剂液滴中 Ge 浓度的差异。每个层中的 Ge 浓度被预测为依赖于前一层的组成。在 25nm 直径的纳米线中，通过在 Si 上生长 x = 0.85 的 Si1-xGex，实现了最陡峭的异质界面（约 5nm）。
