Raman activity and high electron mobility of piezoelectric semiconductor GaSiX₂ (X = N, P, and As) toward flexible nanoelectronic devices

Abstract Inspired by the urgent demand for novel multifunctional materials in advanced technology applications, herein, first-principles calculations are utilized to construct new two-dimensional GaSi X 2 ( X = N, P, As) monolayers. After optimizing the GaSi X 2 crystal structures, their stabilities, Raman responses, piezoelectricity, and electronic/transport characteristics are systematically studied. Results from phonon dispersions, ab initio molecular dynamics simulations, elastic constants, and cohesive energies confirm the good dynamic, thermal, energetic, and mechanical stabilities of the proposed GaSi X 2 monolayers. Based on the Heyd–Scuseria–Ernzerhof approach, the GaSi X 2 exhibit semiconductor behaviors with favorable bandgaps for absorption of the visible spectrum of 1.82 for GaSiP 2 and 1.43 eV for GaSiAs 2 monolayer. In addition, the GaSi X 2 monolayers also show piezoelectric effects, and high in-plane piezoelectric coefficients d 11 are found for the GaSiP 2 (−1.16 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:mi>pm</mml:mi> </mml:mrow> <mml:mstyle scriptlevel="0"/> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">V</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> ) and GaSiAs 2 (−1.26 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:mrow> <mml:mi>pm</mml:mi> </mml:mrow> <mml:mstyle scriptlevel="0"/> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">V</mml:mi> </mml:mrow> <mml:mrow> <mml:mo>−</mml:mo> <mml:mn>1</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> ). The carrier mobilities of the GaSi X 2 are estimated by the deformation potential method for their transport properties. Along two in-plane transport directions, the carrier mobilities of the GaSi X 2 are anisotropy for holes and electrons. GaSiP 2 and GaSiAs 2 show large electron mobilities along the x axis of 2816.99 and 1211.41 cm 2 V −1 s −1 , respectively. Thus, the GaSiP 2 and GaSiAs 2 monolayers not only have high anisotropic electron mobilities but also favorable bandgaps and large piezoelectric coefficients, indicating potential applications of GaSiP 2 and GaSiAs 2 in electronic, photovoltaic, and piezoelectric devices. The findings of this study may provide insights into the GaSi X 2 monolayers for multifunctional applications.