Investigation of AlGaN/GaN HEMT for pH sensing applications and sensitivity optimization

In this work, AlGaN/GaN HEMT pH sensitive response has been presented through extensive simulations demonstrating the effect of pH variation on channel conductance, potential and conduction band profile. The pH solution is defined by an intrinsic semiconductor material whose properties are modified to mimic electrolyte solution and the effect of variation in charged adsorbates is accommodated by adjusting the interface charges density at oxide-semiconductor interface. The effect of AlGaN barrier layer composition (thickness and Aluminum mole fraction) on the sensitivity was analyzed by simulating different device configurations using ATLAS Silvaco device simulation tool. The devices render improved voltage sensitivity (S_V = ΔV_r/pH) and high output current sensitivity (S_I = (ΔI_ds/pH) = 15 mA/mm-pH). The simulations predict a thinner barrier layer along with smaller mole fraction device is most sensitive to pH changes at the surface for an open gate operation.