Black phosphorus (BP) is a promising two-dimensional (2D) material for nanoscale transistors, due to its expected higher mobility than other 2D semiconductors. While most studies have reported ambipolar BP with a stronger p-type transport, it is important to fabricate both unipolar p- and n-type transistors for low-power digital circuits. Here, we report unipolar n-type BP transistors with low work function Sc and Er contacts, demonstrating a record high n-type current of 200 μA/μm in 6.5 nm thick BP. Intriguingly, the electrical transport of the as-fabricated, capped devices changes from ambipolar to n-type unipolar behavior after a month at room temperature. Transmission electron microscopy analysis of the contact cross-section reveals an intermixing layer consisting of partly oxidized metal at the interface. This intermixing layer results in a low n-type Schottky barrier between Sc and BP, leading to the unipolar behavior of the BP transistor. This unipolar transport with a suppressed p-type current is favorable for digital logic circuits to ensure a lower off-power consumption.

中文翻译：

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具有低功函数触点的单极n型黑磷晶体管

黑磷（BP）是一种有望用于纳米级晶体管的二维（2D）材料，因为其预期的迁移率高于其他2D半导体。尽管大多数研究都报告了具有更强p型传输能力的双极性BP，但为低功耗数字电路制造单极性p型和n型晶体管非常重要。在这里，我们报道了具有低功函数Sc和Er触点的单极n型BP晶体管，这证明了在6.5 nm厚的BP中创纪录的200μA/μm的高n型电流。有趣的是，在室温下放置一个月后，制成的加帽设备的电传输会从双极性变为n型单极性行为。接触截面的透射电子显微镜分析揭示了在界面处的混合层，该混合层由部分氧化的金属组成。此混合层导致Sc和BP之间的n型肖特基势垒低，从而导致BP晶体管的单极行为。具有抑制的p型电流的这种单极传输有利于数字逻辑电路，以确保较低的关断功耗。