用于 MoS2 场效应晶体管的 ALD 生长二维 TiSx 金属触点,Nanoscale Advances

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用于 MoS2 场效应晶体管的 ALD 生长二维 TiSx 金属触点
Nanoscale Advances ( IF 4.6 ) Pub Date : 2023-08-15 , DOI: 10.1039/d3na00387f
Reyhaneh Mahlouji ₁ , Wilhelmus M M Erwin Kessels ₁ , Abhay A Sagade ₂ , Ageeth A Bol ₁

Affiliation

_{MoS 2}场效应晶体管 (FET) 的金属触点在器件电气特性中起着决定性作用，需要仔细选择。由于接触/MoS ₂界面处发生肖特基势垒 (SB) 和费米能级钉扎 (FLP) 效应，MoS ₂ FET 经常遭受高接触电阻 ( R _c ) 的困扰。解决这个问题的一种方法是用 2D 对应物取代传统的 3D 块状金属触点。在此，我们研究了二维金属 TiS _x ( x ∼ 1.8) 作为 MoS ₂ FET 的顶部接触。我们采用原子层沉积 (ALD) 来合成 MoS ₂通道以及 TiS _x触点，并评估所制造器件的电气性能。_{在MoS 2}上生长不同厚度的TiS _x，并将所得器件与具有传统Ti金属接触的器件进行电学比较。_{我们的研究结果表明，仅用约 1.2 nm 的 2D TiS x}替换 5 nm Ti 块状接触有利于改善整体器件指标。_利用这种超薄 TiS _x触点，导通状态电流 ( ION ) 增加三倍并增加至~35 μA μm ^-1。R _c也减少了四倍并达到~5 MΩ μm。_{尽管认为在TiS x} /MoS ₂界面处形成的SB高于在Ti/MoS ₂界面处形成的SB，但仍观察到这种性能增强。_{因此，这些器件指标的改进可能主要与MoS 2}中静电掺杂水平的增加有关，这是由于使用2D TiS _x来接触2D MoS ₂的结果。TCAD 设备模拟也很好地支持了我们的发现。

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ALD-grown two-dimensional TiSx metal contacts for MoS2 field-effect transistors

Metal contacts to MoS₂ field-effect transistors (FETs) play a determinant role in the device electrical characteristics and need to be chosen carefully. Because of the Schottky barrier (SB) and the Fermi level pinning (FLP) effects that occur at the contact/MoS₂ interface, MoS₂ FETs often suffer from high contact resistance (R_c). One way to overcome this issue is to replace the conventional 3D bulk metal contacts with 2D counterparts. Herein, we investigate 2D metallic TiS_x (x ∼ 1.8) as top contacts for MoS₂ FETs. We employ atomic layer deposition (ALD) for the synthesis of both the MoS₂ channels as well as the TiS_x contacts and assess the electrical performance of the fabricated devices. Various thicknesses of TiS_x are grown on MoS₂, and the resultant devices are electrically compared to the ones with the conventional Ti metal contacts. Our findings show that the replacement of 5 nm Ti bulk contacts with only ∼1.2 nm of 2D TiS_x is beneficial in improving the overall device metrics. With such ultrathin TiS_x contacts, the ON-state current (I_ON) triples and increases to ∼35 μA μm⁻¹. R_c also reduces by a factor of four and reaches ∼5 MΩ μm. Such performance enhancements were observed despite the SB formed at the TiS_x/MoS₂ interface is believed to be higher than the SB formed at the Ti/MoS₂ interface. These device metric improvements could therefore be mainly associated with an increased level of electrostatic doping in MoS₂, as a result of using 2D TiS_x for contacting the 2D MoS₂. Our findings are also well supported by TCAD device simulations.

更新日期：2023-08-15

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