Research On AlGaN/GaN HEMT Biochemical Sensor With High Density Biomolecular Film Gate

The development of science and technology further accelerate the globalization.While high-level globalization creates huge wealth for mankind,it also increases the possibility of the pandemic of infectious diseases,which could bring a great threat to human life.Under this circumstance,fast and accurate real-time detection technology becomes a more important technology.Biochemical sensors based on field effect transistors have broader application prospects in the field of real-time detection due to their advantages of miniaturization,integration and rapid response.AlGaN/GaN HEMT biochemical sensor is an emerging biochemical detection technology,which shares the advantages of fast detection speed,high sensitivity,and corrosion resistance.Lots of researches has conducted on AlGaN/GaN HEMT biochemical sensors since the first one was proposed in 2001,however,little effort has been paid on the surface modification scheme of AlGaN/GaN HEMT.The modification of biomolecular membrance on the surface of sensing area suffers from low density and poor repeatability,which affects the performance of the sensor a lot.To well handle this problem,researches on high-performance biomolecular gated AlGaN/GaN HEMT biochemical sensors were carried out and specified in this thesis.The specific research contents are as follows:1.Design and fabrication of AlGaN/GaN HEMT devices for biochemical sensingA physical model of AlGaN/GaN HEMT sensor was built by analyzing the polarization effect of AlGaN/GaN heterojunction materials and the formation and properties of two-dimensional electron gas.The structure of AlGaN/GaN HEMT device is designed by calculation and simulation,where the length and the width of the sensing area is 100 ?m and 500 ?m respectively.Moreover,a device with excellent performance that can be used for biochemical sensing was prepared after optimizing the key process of device preparation.2.Research on AlGaN/GaN HEMT biochemical sensor with high density biomolecular film gateThe performance of biomolecular film gate AlGaN/GaN HEMT biochemical sensor is limited by inefficient modification of biomolecular.To solve this problem,the ethanolamine monolayer was proposed for high-density biomolecular modification on GaN oxide.The modification efficiency of ethanolamine was characterized by contact angle and nano-gold adsorption experiments.The modified GaN oxide was used as sensing film for pH detection to characterize the better modification efficiency of ethanolamine,where the sensitivity of which is nearly two times higher than that of the APTES modified one.The ethanolamine modified area of the sensor was further functionalized by prostate-specific antibody biomolecular for prostate-specific antigen detection.The results show that the sensitivity of ethanolamine modified one is increased more than three time compared to that of APTES modified one at 1 ng·mL-1,while the limit of detection is as low as 1 fg·mL-1.Using ethanolamine as the surface modification scheme of biomolecular film gate AlGaN/GaN HEMT can effectively improve the modification efficiency and further enhance the sensitivity of the sensor.3.Research on disposable type molecular film gate AlGaN/GaN HEMT pH sensorThe repeated modification and testing processes of biomolecular film gate AlGaN/GaN HEMT biochemical sensor could affect the stability and sensitivity of the sensor.The disposable structure,where the sensing area and the HEMT are separated,was used to avoid the direct contact between the HEMT and the electrolyte.However,the existing disposable gated AlGaN/GaN HEMT biochemical sensor suffered problems such as poor stability of sensitive material and low modification efficiency of biomolecular,which finally affects the performance of the sensor.ZnO nanorods were proposed as the sensing material for AlGaN/GaN HEMT for its high specific surface area and good biochemical testing application.However,bare ZnO nanorods tend to be corroded in acid and alkaline environments,which limits its application.Under this circumstance,the modification of ethanolamine on ZnO nanorods was proposed to not only protect them from being corroded in acidic and alkaline solutions,but also enhance the sensitivity of the sensor.The principle of the enhanced performance is analyzed from the perspective of energy band modulation and the research on the surface modification of ethanolamine on sensing material is extended from experiment to theory,therefore the superiority of the ethanolamine modification scheme is fully demonstrated.