Highly stable two-dimensional gold selenide with large in-plane anisotropy and ultrahigh carrier mobility

Abstract

The discovery of 2D anisotropic semiconductors with high carrier mobility is critical for highly efficient polarization-sensitive devices. Here, we explore the unique properties of an unexpected, yet highly-promising 2D chalcogenide, gold selenide (AuSe) with high stability, ultrahigh and anisotropic carrier mobilities. Linear (Au^II) and square-planar (Au^IV) channels coexist in 2D AuSe, leading to the remarkable in-plane anisotropy. Electrons favour transport along the a direction with mobility up to 3.98 × 10⁴ cm² (V s)⁻¹, whereas hole mobility along the b direction (over 8000 cm² (V s)⁻¹) is almost 40 times larger than that along the a direction. The carrier mobility of 2D AuSe is much higher than most widely-studied 2D semiconductors, such as MoS₂ and phosphorene. Moreover, 2D AuSe shows almost full spectral solar absorption, relying on the proper bandgaps. The combination of the separation of ultrafast electron and hole transport channels (Au^IV and Au^II) and efficient solar absorption enables 2D AuSe great potentials in multifunctional optoelectronics.