An analytical and experimental biosensor for human MIG using AlGaN/GaN based HEMT devices

An amperometric biosensor using AlGaN/GaN based HEMT devices is constructed experimentally and validated through analytical and numerical techniques for detection of a key protein in allograft rejection (Human MIG/CXCL9). The prototype developed provides a reliable sensing platform that will allow label-free and marker-free detection. By exploiting characteristics unique to AlGaN/GaN based HEMT devices, a floating gate configuration is employed to allow reliable sensing without the need for any reference electrode. Self-assembled monolayers (SAM) are formed at the gate surface by using a crosslinker (DSP) to allow for appropriate immobilization of target antibodies. A theoretical analytical and numerical model is developed to explain the mechanism of action of the proposed biosensor. Furthermore, other issues such as repeatability, influence of the substrate, threshold shifting, and device packaging are addressed. Finally, an experimental circuit is constructed with the previously prepared biosensor to validate the claims made in this thesis

Characteristics of AlGaN/GaN HEMTs for Detection of MIG

The aim of this research work is to analyze the surface characteristics of an improved AlGaN/GaN HEMT biosensor. The investigation leads to analyze the transistor performance to detect human MIG with the help of an analytical model and measured data. The surface engineering includes the effects of repeatability, influence of the substrate, threshold shifting, and floating gate configuration. A numerical method is developed using the charge-control model and the results are used to observe the changes in the device channel at the quantum level. A Self-Assembled Monolayer (SAM) is formed at the gate electrode to allow immobilization and reliable crosslinking between the surface of the gate electrode and the antibody. The amperometric detection is realized solely by varying surface charges induced by the biomolecule through capacitive coupling. The equivalent DC bias is 6.99436 × 10−20 V which is represented by the total number of charges in the MIG sample. The steady state current of the clean device is 66.89 mA. The effect of creation and immobilization of the protein on the SAM layer increases the current by 80 - 150 μA which ensures that successful induction of electrons is exhibited