亚50纳米沟长的准弹道输运黑磷晶体管

Recently, black phosphorus has joined the two-dimensional material family as a promising candidate for electronic and photonic applications due to its moderate bandgap, high carrier mobility, and unusual in-plane anisotropy. Although there are some studies on black phosphorus, they are mainly focused on the low field transport properties, the metal-semiconductor Schottky contact, and structural defect-induced scattering. The overall assessment of technological relevant parameters such as output capability, high-field transport, and ballistic transport are still lacking, and their limiting factors are yet to be discussed. In this proposal, we aim to realize ballistic transport in sub-50 nm black phosphorus transistors and study its high-field transport mechanisms. We will use ultra-thin high-k materials to replace the traditional SiO2 and novel device structure as well as the crystal orientation engineering to realize short-channel black phosphorus transistors with ballistic transport. And based on this, we will further carry out a series of approaches to improve the carrier velocity for high performance devices, including heating effect and phonon effect. Finally, the low-frequency noise characteristics of short-channel black phosphorus transistors under low temperature will be explored to study the reliability and carrier scatter mechanism. The implementation of this project will provide a solid scientific basis for the building of novel device structure by two-dimensional materials for future information devices.

近来，二维半导体黑磷材料因具有直接带隙、优异的电子迁移率以及各向异性等良好性能，在电子和光学等领域具有广阔的应用价值和研究价值。虽然关于黑磷器件的研究已经有一些报道，但是大多数研究集中在低场下的载流子输运以及优化迁移率的研究。关于黑磷短沟道器件的高场载流子输运机制与速度极限并未得到有效验证。本课题拟探索黑磷载流子在高场的输运机制及弹道输运实现方法，研究其弹道率极限的机理与瓶颈。通过优化界面特性，采用超薄高介电材料代替传统的二氧化硅，结合器件结构的创新和晶向工程，探索其高场输运机制，实现亚50纳米沟长的准弹道输运黑磷器件。在此基础上，研究载流子速度退化的机制，并提出从热效应和声子效应两个方面来抑制载流子速度退化的方法。最终，本课题将研究低温条件下短沟道黑磷器件的低频噪声性能，进一步研究其载流子散射机制。本项目的实施将有望为新型二维材料的器件构筑以及在未来信息器件的应用提供重要的科学依据。

二维半导体黑磷材料因具有直接带隙、优异的电子迁移率以及各向异性等良好性能，在未来电子器件领域具有广阔的应用价值和研究价值。通过优化界面工程和设计载流子输运方向沿着迁移率最大的扶手椅（armchair）方向。对于沟长为100 nm的黑磷晶体管，其室温驱动电流达到1.2 mA/μm，20 K时进一步提高到1.6 mA/μm。室温下黑磷的空穴饱和速度为1.5 × 10^7 cm/s。基于如此性能的器件，成功实现了弹道输运。通过Virtual Source模型提取了黑磷晶体管的弹道率。室温下100 nm的黑磷晶体管的弹道率达到36%，高于同等参数下硅基MOS器件。在低温20 K时，弹道率提高到了79.4%。模型计算预测在20 K时，沟长为10 nm的黑磷晶体管的弹道率接近100%。为了降低器件功耗，提出了一种由二维黑磷/氧化铝/黑磷结构制成的高效隧穿器件。这个结构中的隧穿载流子相对于驱动电流是横向输运的，具有改善的输出电流密度的潜力。并且由隧穿载流子引起的静电效应可以显著地通过绝缘层调节沟道载流子密度，从而产生巨大的负微分电阻现象。此外，该隧穿晶体管能够在360 K至70 K的温度范围内以仅为玻尔兹曼极限1/10的体因子（栅极电压相对变化与表面电势相对变化的比值）进行电流陡峭开关。最后，在高热导率的氧化铍介质上制备的高性能晶体管器件，与栅介质为氧化铪的晶体管相比，有效提高了器件的热扩散并抑制了自热效应。