Dielectric-Modulated Nanogap Engineered AlGaN/GaN MOSHEMT: A High-Performance Platform for Neutral and Charged Biomolecule Detection.

Abstract

This work presents a dielectric-modulated AlGaN/GaN Metal-Oxide-Semiconductor High Electron Mobility Transistor (MOSHEMT) biosensor incorporating an embedded nanocavity positioned adjacent to the drain, designed for sensing biomolecules that are either neutral or carry a net charge. Device behaviour is simulated using the Silvaco ATLAS framework with advanced physical models to accurately capture electrostatic and carrier transport phenomena. Neutral biomolecules are modelled through their dielectric permittivity, whereas charged biomolecules are represented by both their dielectric constant and specified surface charge densities (ρ, in cm⁻²) at the nanocavity interface. Sensitivity is assessed using the threshold voltage (V_th) shift and the fluctuation of the drain current (I_D), with reference cases being air (ε = 1) and a charge-neutral state (ρ = 0). Among all neutral analytes, keratin exhibited the highest sensitivity, while negatively charged biomolecules demonstrated greater modulation of device characteristics compared to positively charged ones. Detailed analysis of energy band diagrams (EBDs), channel potential profiles, transconductance, and channel conductance confirms the influence of both dielectric and charge modulation on device performance. The implication of the Al mole fraction and cavity length variations on device performance is also systematically analyzed, revealing their role in enhancing electrostatic control and sensitivity. The proposed architecture achieves significant improvements in sensing metrics compared to reported GaN-based biosensors, underscoring its efficacy as a high-sensitivity, platform for next-generation biomedical detection applications.