Analytical model for DG-AlGaN/GaN MOS-HEMT for sensitive analysis of pH analytes and charged biomolecules

Abstract

This article introduces an analytical model for double-gate AlGaN/GaN MOS-HEMT biosensors to accurately detect pH analytes and charged biomolecules. The device incorporates nanocavities and operates on the concept of dielectric modulation, presuming the presence of a native oxide layer on the surface of the AlGaN layer. The pH of the analyte is represented as the interface charge. Numerical simulations evaluate the biosensor's effectiveness by analyzing its sensitivity to drain ON current (S_I) and threshold voltage (S_V). The device exhibited a peak S_V of 586.5 mV, a value tenfold more significant than the Nernst limit for pH analyte. The maximum S_I, computed at the peak transconductance, was determined to be 135.5 mA/mm/pH at V_G = −2V and V_D = 5V. The biosensor response to a charged biomolecule is assessed by considering the dielectric constant and charge density (ρ). The biosensor exhibited a maximum S_I of 0.225 at V_D = 5V and V_G = −1V and S_V of 1.488V for charged biomolecule at ρ = 1 × 10¹²/cm². The impact of the bias voltages, ion molar concentration of pH analyte, AlGaN layer thickness and cavity length on the S_I of the device is explored in detail. The S_I for pH analytes is unaffected by the AlGaN layer thickness but enhanced with ion molar concentration and cavity length. However, for charged biomolecules, S_I decreased with increased AlGaN layer thickness and improved with cavity length.