Low contact resistance and electrical transport improvement obtained by surface adsorption strategy in blue phosphorene field-effect transistor

Two-dimensional semiconductors have been identified as promising channel materials in nanoelectronic devices for sustaining Moore's law. Searching for suitable metal electrodes is critical to fabricating high-performance nanoscale channel field-effect transistors (FETs). In the present article, we adopt first-principles calculations to explore adsorption energy, adsorption structures, and electronic structures of H, Li, B, C, N, O, F, and Na adsorption on monolayer blue phosphorene (BlueP). Our calculated results indicate that all adatoms have minor impacts on the structure of BlueP except for B, C, and F adatoms. H, Li, Na, and N adsorption results in metallic properties of adsorption systems, but O adsorption preserves its semiconductor property. We also use density functional theory coupled with the nonequilibrium Green function method to investigate the transport properties of BlueP-based FETs with Li-adsorbed and Na-adsorbed BlueP electrodes. Our calculated results indicate that Li-adsorbed BlueP is superior to Na-adsorbed BlueP. Especially, BlueP-based FET with 9 nm channel length exhibits an excellent on-state current of $\ensuremath{\approx}1540.3\phantom{\rule{0.28em}{0ex}}\textmu{}\mathrm{A}/\textmu{}\mathrm{m}$, distinctly exceeding the International Technology Roadmap for Semiconductors requirements for high-power devices. These results imply that Li-adsorbed BlueP may act as an appropriate electrode material for BlueP-based FETs, meaning that low contact resistance can be obtained by surface adsorption strategy. In addition, the results of carrier density, device conductance, projected density of states, and real-space scattering state show that O adsorption on BlueP channel can improve the electrical transport performance of the device. This implies that absorbing suitable elements on the semiconductor channel can effectively improve device performance, thus providing guidance for the design of future FETs.