First-principles study of Janus TeWZH (Z = N, P, As) monolayers: vibrational behaviors and Raman activity, piezoelectricity, electronic properties, and carrier mobility.

In this work, we systematically investigate the structural, vibrational, electronic, and transport properties of a series of novel Janus TeWZH (Z = N, P, As) monolayers using density functional theory. Our results confirm that these materials are structurally stable and exhibit semiconducting behavior with band gaps ranging from 1.42 to 2.19 eV at the HSE06 level of theory (calculated without spin-orbit coupling). Key findings include significant valence band splitting at the K-point (up to 0.49 eV) induced by strong spin-orbit coupling, and a robust out-of-plane piezoelectric response (with a d 31 coefficient reaching 0.68 pm V-1) induced by the broken mirror symmetry of the Janus structure. Furthermore, we find that while these monolayers possess relatively low carrier mobilities, their transport dynamics are primarily governed by acoustic deformation potential scattering, which acts as the dominant phonon-limited mechanism for both electrons and holes. These findings position Janus TeWZH materials as promising candidates for spintronic and piezoelectric nanodevices.