Black Phosphorus Field-Effect Transistors with Work Function Tunable Contacts

Abstract

Black phosphorus (BP) has been recently rediscovered as an elemental two-dimensional (2D) material that shows promising results for next generation electronics and optoelectronics because of its intrinsically superior carrier mobility and small direct band gap. In various 2D field-effect transistors (FETs), the choice of metal contacts is vital to the device performance, and it is a major challenge to reach ultralow contact resistances for highly scaled 2D FETs. Here, we experimentally show the effect of a work function tunable metal contact on the device performance of BP FETs. Using palladium (Pd) as the contact material, we employed the reaction between Pd and H to form a Pd-H alloy that effectively increased the work function of Pd and reduced the Schottky barrier height (Φ) in a BP FET. When the Pd-contacted BP FET was exposed to 5% hydrogen concentrated Ar, the contact resistance (R) improved between the Pd electrodes and BP from ∼7.10 to ∼1.05 Ω·mm, surpassing all previously reported contact resistances in the literature for BP FETs. Additionally, with exposure to 5% hydrogen, the transconductance of the Pd-contacted BP FET was doubled. The results shown in this study illustrate the significance of choosing the right contact material for high-performance BP FETs in order to realize the real prospect of BP in electronic applications.

High Mobility Anisotropic Black Phosphorus Nanoribbon Field‐Effect Transistor

“…After the hydrogen treatment, the contact resistance at ZZ interface reduces from 3.59 to 1.48 Ω mm, which approaches the AC‐oriented contact resistance of 1.38 Ω mm. Moreover, this value is comparable to bulk BP‐FET with palladium (Pd) contact (1.05 Ω mm) after Pd–H alloy formation and even smaller than previously reported thermally evaporated Ni contact resistance of 3.15 and 3.73 Ω mm . By physically sputtering the S/D area and treating the Ni contact with forming gas, the Ni contact resistance has been reduced to a record low value.…”

Black phosphorus electronics

“…Palladium (Pd) was reported to have high hydrogen solubility. Thus, it has been employed to reduce the SBH of BP FETs [71]. The contact resistance of Pd-contacted few-layer BP FET with different H 2 concentrations is displayed in Fig.…”

Visualizing Degradation of Black Phosphorus Using Liquid Crystals

“…Due to its unique electronic structure, BP has also shown excellent performance in optoelectronics and memory devices 5 – 7 . BP shows both a p and an n-type behaviour as well as ambipolar transport characteristics depending upon the contact metal used 3 .…”