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

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 × 10 12 /cm 2 . 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. • A mathematical model for DG AlGaN/GaN MOS-HEMT for detecting accurately pH analytes and charged biomolecules is proposed. • The surface charge calculations at the AlGaN layer include the effects of stern and native oxide layers. • The threshold voltage sensitivity of the proposed biosensor is two times more than the double gate ISFET. • The model can detect pH analytes, with the maximum and minimum S I of 135.5 mA/mm/pH and 113.2 mA/mm/pH, at pH = 2 and 12, respectively. • The device exhibited excellent drain current sensitivity of 0.225 at ρ = 1 × 10 12 cm 2 .