Raman response, piezoelectricity, and transport properties of the two-dimensional Janus HfSi⁢𝑋3⁢H (𝑋=N/P/As) semiconductors: A first-principles stud

Abstract

Exploring advanced materials with extraordinary properties is necessary for developing high-performance devices. In this work we construct two-dimensional Janus $H f S i 𝑋 3 H (𝑋 = N / P / A s)$ monolayers and systematically examine their physical properties by utilizing first-principles calculations. Specifically, we focus on the stabilities, Raman spectra, electronic structures, piezoelectricity, and transport properties of the monolayers. As a result, the studied $H f S i N 3 H, H f S i P 3 H$ , and $H f S i A s 3 H$ monolayers are found as semiconductors with good structural, mechanical, dynamic, and thermodynamic stabilities. The piezoelectric coefficients ( $𝑒 11$ and $𝑒 31$ ) are calculated to examine the piezoelectricity of the $H f S i 𝑋 3 H$ monolayers. It is noted that besides the in-plane piezoelectricity, the three monolayers show additional out-of-plane piezoelectric effects because of their noncentrosymmetric structures. We also include fully anisotropic acoustic deformation potential, ionized impurity, piezoelectric, and polar electron–phonon scattering to calculate the total carrier mobilities of Janus $H f S i 𝑋 3 H$ . It is demonstrated that Janus $H f S i 𝑋 3 H$ monolayers exhibit low carrier mobilities at room temperature $(< 100 c m 2 V - 1 s - 1)$ . Scattering from polar optical phonons is found to dominate the total mobilities of both electrons and holes.