Black Phosphorus Field-Effect Transistors with Work Function Tunable Contacts

5 years ago

Black Phosphorus Field-Effect Transistors with Work Function Tunable Contacts

Tom Nilges, Chongwu Zhou, Zhen Li, Liang Chen, Anyi Zhang, Chenfei Shen, Yihang Liu, Ahmad N. Abbas, Yuqiang Ma, Qingzhou Liu, Moh. R. Amer, Jihan Chen

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 H₂ to form a Pd–H alloy that effectively increased the work function of Pd and reduced the Schottky barrier height (Φ_B) in a BP FET. When the Pd-contacted BP FET was exposed to 5% hydrogen concentrated Ar, the contact resistance (R_c) 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.

Publisher URL: http://dx.doi.org/10.1021/acsnano.7b02858

DOI: 10.1021/acsnano.7b02858