Enhancement of sensing performance of GaN-based MOS-HEMT biosensors by graded AlGaN barrier

To improve the sensing performance, the GaN-based MOS-HEMT biosensor with graded AlGaN barrier was proposed and investigated by Silvaco TCAD. The simulation results indicate that the proposed device exhibits higher sensitivity than that with conventional AlGaN barrier. Furthermore, the impact of graded AlGaN barrier layer thickness (15 nm - 30 nm) and maximum Al mole fraction (0.1 - 0.25) was investigated systematically to optimize sensing sensitivity. It is demonstrated that the sensitivity of MOS-HEMT biosensors can be enhanced by decreasing the thickness or increasing the maximum Al mole fraction of graded barrier layer. This can be mainly attributed to the variation of carrier concentration and energy band structure in the MOS-HEMT heterostructure. In addition, the effect of biomolecule filling rate in the cavity on device performance was also studied. It is found that the sensitivity increases with the biomolecule filling rate. In the ideal state of 100% biomolecule filling rate, the sensing currents of MOS-HEMT biosensor reached 72.8 mA/mm, 154.9 mA/mm, 238.6 mA/mm, 351.8 mA/mm, and 399.3 mA/mm for Uricase, Streptavidin, Biotin, ChOx, and APTES biomolecules, respectively, which are superior than previous reported MOS-HEMT biosensors. This work provides fundamental support for the development of highly sensitive GaN-based MOS-HEMT biosensors.