A novel back gated GaN/AlGaN HEMT structure for biological sensing applications

In this paper, a novel back gated AlGaN/GaN High Electron Mobility Transistor (HEMT) structure is proposed for detection of biological molecules such as nucleic acids (DNAs, RNAs). The proposed device consists of a thin film layer of AlGaN on top of a GaN thin film layer grown on a substrate such as sapphire or silicon, wherein the substrate is completely back etched exposing the GaN surface for attachment of nucleic acid molecules. Numerical study of this proposed device was carried out using TCAD Silvaco ATLAS to study the effect of attachment of nucleic acid molecules on the GaN surface. As the single-stranded and double-stranded DNA and RNA molecules are negatively charged, their attachment on the GaN surface leads to a variation of 2DEG gas on the AlGaN/GaN interface and therefore on the drain current. The performance of this structure is compared with an equivalent silicon MOS transistor and also with a conventional front gated HEMT structure. The proposed device shows a better sensitivity to presence of nucleic acid molecules in both the cases.