Dopant-Engineered Monolayer InAs: Linking Structural Modulation to Gas Adsorption and Optoelectronic Behavior

While bulk indium arsenide (InAs) exhibits excellent electronic properties, its application is hindered by lattice mismatch with substrate and limited surface tunability. These challenges motivate the exploration of few-layer InAs, which offers distinct advantages in flexibility and surface reactivity. In this study, we perform a comprehensive first-principles investigation of how various substitutional dopants and vacancies affect the structural, opto-electronic, mechanical, and chemical properties of monolayer InAs. Transition metal dopants such as Co and Fe induce moderate bandgap increment and reduced in-plane stiffness, while Se and Pd enhance out-of-plane rigidity. These modifications influence electron localization and band alignment. Optical absorption is broadened in the infrared region due to sub-bandgap transitions. Gas adsorption analyses reveal that dopants such as Co, Fe, and P significantly strengthen binding and charge transfer with gas molecules like NO₂ and NH₃. This work highlights dopant-modulated structure-property coupling in 2D InAs and provides design insights for tunable optoelectronic and sensing applications.