Atomically thin semiconducting penta-PdP2 and PdAs2 with ultrahigh carrier mobility

Abstract

It is highly desirable to reach a high carrier mobility in two-dimensional (2D) atomic crystals with a modest band gap for electronic applications. In this study, two 2D semiconducting materials, penta-PdX₂ (X = P, As), are found to be promising candidates to approach this goal. Both penta-PdP₂ and penta-PdAs₂ have a band gap of about 0.7–0.8 eV. Their carrier mobility is up to 10⁴ cm² V⁻¹ s⁻¹ for electrons and 10⁵ cm² V⁻¹ s⁻¹ for holes, among the highest in 2D semiconductors. Moreover, the effective mass and band gap can be effectively tuned by applying a biaxial strain. The electron effective mass climbs up firstly and then largely declines under tensile load with a turning point at 5% for penta-PdP₂ and 2% for penta-PdAs₂. Furthermore, penta-PdX₂ monolayers exhibit strong optical absorption in a wide wavelength range. All these outstanding properties render penta-PdX₂ promising candidates for ultra-fast electronic and optoelectronic applications.