Piezoelectric GaGeX (X = N, P, and As) semiconductors with Raman activity and high carrier mobility for multifunctional applications: a first-principles simulation.

In the present work, we propose GaGeX (X = N, P, As) monolayers and explore their structural, vibrational, piezoelectric, electronic, and transport characteristics for multifunctional applications based on first-principles simulations. Our analyses of cohesive energy, phonon dispersion spectra, and molecular dynamics simulations indicate that the three proposed structures have good energetic, dynamic, and thermodynamic stabilities. The GaGeX are found as piezoelectric materials with high piezoelectric coefficient of -1.23 pm V for the GaGeAs monolayer. Furthermore, the results from electronic band structures show that the GaGeX have semiconductor behaviours with moderate bandgap energies. At the Heyd-Scuseria-Ernzerhof level, the GaGeP and GaGeAs exhibit optimal bandgaps for photovoltaic applications of 1.75 and 1.15 eV, respectively. Moreover, to examine the transport features of the GaGeX monolayers, we calculate their carrier mobility. All three investigated GaGeX systems have anisotropic carrier mobility in the two in-plane directions for both electrons and holes. Among them, the GaGeAs monolayer shows the highest electron mobilities of 2270.17 and 1788.59 cm V s in the and directions, respectively. With high electron mobility, large piezoelectric coefficient, and moderate bandgap energy, the GaGeAs material holds potential applicability for electronic, optoelectronic, piezoelectric, and photovoltaic applications. Thus, our findings not only predict stable GaGeX structures but also provide promising materials to apply for multifunctional devices.