Study On The Key Technology Of GaN Based Biosensor

Biosensing technology is the cutting-edge science and technology in today society,and it is an intersecting comprehensive discipline integrating electronics,biology,medical treatment,chemistry,physics,and materials.Biosensors have been highly valued and widely used in various fields such as environmental monitoring,medical tracking,and food safety.The wide band gap and strong chemical hardness of gallium nitride ensure that it can exist stably in harsh environments such as high temperature,acid and alkali;at the same time,the AlGaN/GaN heterojunction forms a high-concentration,high-mobility two-dimensional electron gas(2DEG)through the polarization effect,the concentration of 2DEG is extremely sensitive to the AlGaN/GaN heterojunction surface,which is very conducive to the induction of weak biological signals.The on-resistance of GaN-based biosensors is two orders of magnitude lower than that of Si,and about an order of magnitude lower than that of Si C.Low on-resistance can reduce conduction loss and improve detection sensitivity.The on-resistance of AlGaN/GaN heterojunction sensors is mainly composed of channel resistance and contact resistance.Therefore,reducing contact resistance is particularly important for improving detection sensitivity.In the process of device preparation,the damage caused by the mesa isolation leads to high leakage current and thus reduces the detection sensitivity.This paper needs to reduce the leakage current to improve the detection sensitivity.In this paper,by improving the preparation process of gallium nitride-based biosensors to improve its sensing performance,the key process optimization is mainly from the two aspects of reducing ohmic contact resistance and isolating leakage current.The main research contents and results are as follows:(1)First,by comparing the ohmic contact resistance changes of the samples before and after the ICP oxygen plasma surface treatment,it is determined that the oxygen plasma treatment can effectively reduce the contact resistance.By comparing the contact resistance values under different conditions,it is found that the contact resistance can be effectively reduced by increasing a certain amount of ICP power and RF power,and finally the optimal conditions(ICP:250 W,RF:60 W,0.8 Pa,O₂:30 sccm,time:5 min);reduce the ohmic contact resistance from 1.31?·mm to 0.41?·mm,which is about 69%lower than the contact resistance of the reference sample.Using atomic force microscopy(AFM),photoluminescence spectroscopy(PL)and energy dispersive X-ray spectroscopy(EDX)to characterize and analyze the samples before and after oxygen plasma treatment,it was found that nitrogen vacancies(V_N)were added to the surface of the treated samples.Increase the doping concentration,narrow the space charge region,facilitate electron tunneling,and reduce ohmic contact resistance.(2)In view of the high leakage current after the isolation of the mesa,the effects of surface treatment methods such as oxidation,"nitrogen supplementation",UV(ozone)light,HCl removal of surface oxides and annealing on the leakage current have been studied.It is found that the leakage current of the sample after rapid thermal annealing(RTA)treatment is at the same level as the leakage current of the bulk material itself.Then the specific conditions are optimized mainly for the microwave annealing technology,and the reasons for the reduction of table leakage are analyzed.The microwave annealing treatment method is studied.The surface leakage current has been reduced from 1×10^-9A/mm to 4.03×10^-10A/mm under a200V DC bias,which is one order of magnitude lower than the leakage current of the bulk material sample.(3)Finally,the optimized oxygen plasma treatment process and the best annealing conditions were used to prepare a GaN-based biosensor,and the pH value biosensor was tested.The sensitivity can reach 1.05m A/pH.