Structural and Electrical Properties of Bilayer SiX (X= N, P, As and Sb)

TL;DR

This study uses density functional theory to explore the structural, electrical, and optical properties of bilayer SiX (X= N, P, As, Sb), revealing strain-tunable bandgaps and unique electronic features like Mexican hat dispersion.

Contribution

It provides a comprehensive analysis of bilayer SiX materials, including their structural configurations, strain effects on bandgap tuning, and optical properties, which were not previously detailed.

Findings

Bilayer SiX are indirect semiconductors.

Tensile strain increases the bandgap; compressive strain causes semiconductor-metal transition.

Bilayer SiSb shows highest pressure sensitivity of the bandgap.

Abstract

In this work, the structural, electrical, and optical properties of bilayer SiX (X= N, P, As, and Sb) are studied using density functional theory (DFT). Five different stacking orders are considered for every compound and their structural properties are presented. The band structure of these materials demonstrates that they are indirect semiconductors. The out-of-plane strain has been applied to tune the bandgap and its electrical properties. The bandgap increases with tensile strain, whereas, compressive strain leads to semiconductor-to-metal transition. The sensitivity of the bandgap to the pressure is investigated and bilayer SiSb demonstrates the highest bandgap sensitivity to the pressure. These structures exhibit Mexican hat-like valence band dispersion that can be approved by a singularity in the density of states. The Mexican-hat coefficient can be tuned by out-of-plane strain. Optical absorption of these compounds shows that the second and lower valence bands due to the high density of states display a higher contribution to optical transitions.