Two-dimensional (2D) $M{A}_2{Z}_4$-family monolayers (MLs) have emerged as promising semiconductors due to their element tunability and rich electronic and optoelectronic properties. In this work, using first-principles calculations, we investigate the electronic, mechanical, transport, and optoelectronic properties of ${\mathrm{WGe}}_2{\mathrm{N}}_4$ ML with a small indirect bandgap. Various nanodevices based on ${\mathrm{WGe}}_2{\mathrm{N}}_4$ ML are studied, including pn-junction diodes, pin-junction field-effect transistors (FETs), and phototransistors. The present results reveal that the ${\mathrm{WGe}}_2{\mathrm{N}}_4$ ML exhibits high rigidity, thermal stability, and remarkable light absorption. These nanodevices demonstrate excellent performance: (1) the pn-junction diode shows a high rectification ratio and a near-Shockley-limit ideality factor, (2) the pin-junction FET exhibits significant gate voltage modulation capability with subthreshold swing as low as 71 mV/dec (close to the theoretical limit calculated based on the Boltzmann distribution), and (3) the phototransistor displays strong optoelectronic responses in the visible and ultraviolet regions. These findings establish ${\mathrm{WGe}}_2{\mathrm{N}}_4$ ML as a versatile platform for developing high-performance, multifunctional nanoelectronic and optoelectronic devices, significantly expanding the application potential of $M{A}_2{Z}_4$-family materials.

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• Electronic structure
• Optoelectronics
• Quantum transport
• 2-dimensional systems
• Devices
• Semiconductor compounds
• Density functional calculations
• Nonequilibrium Green's function