Research On AlGaN/GaN HEMT Sensor For Hydrogen Detection

As an environment-friendly energy,hydrogen is widely used in many fields,such as automobile,military,chemical industry,etc.The inflammability and explosibility of hydrogen hinder its application.Therefore,it is necessary to develop a high-performance hydrogen sensor to detect the storage,transportation and use of hydrogen.The AlGaN/GaN HEMT hydrogen sensor has many advantages,such as fast response,high sensitivity,small volume,easy integration and can work at room temperature,which makes it become a research hotspot in the field of new sensors.In the actual use of the AlGaN/GaN HEMT hydrogen sensor,it will face a variety of environments,so it is particularly important to research the impact of environmental factors on the response characteristics of the sensor.In this paper,AlGaN/GaN HEMT hydrogen sensor was fabricated based on MEMS technology,and the performance test platform of the gas sensor was built independently.The influence of environmental factors(different hydrogen concentration,operating voltage,temperature,pressure,etc.)on the response characteristics of AlGaN/GaN HEMT hydrogen sensor was systematically studied,which provided a certain reference value for the application of AlGaN/GaN HEMT hydrogen sensor in complex and variable environment.The main results are as follows:(1)AlGaN/GaN HEMT hydrogen sensor with Pt-gate was fabricated on an AlGaN/GaN epitaxial wafer.The sensor was fabricated by a series of micro-nano processing technologies,such as photolithography,coating,metal stripping,source isolation,annealing,etc.The sensor size was 1× 1 mm2,the gate Pt thickness was 10 nm,and the gate length was 10 ?m.(2)The response characteristics of AlGaN/GaN HEMT hydrogen sensors under different hydrogen concentrations(25-900 ppm)was studied.The research results showed that:the hydrogen concentration was 25 ppm,hydrogen sensor response sensitivity was 65.9%,the response time was 15 s.As the hydrogen concentration increased from 25 ppm to 900 ppm,hydrogen sensor response sensitivity increased by 14%.The response sensitivity of the sensor was linear with the logarithm of hydrogen concentration.(3)The influence of different operating voltages on the response characteristics of AlGaN/GaN HEMT hydrogen sensor was studied.The results showed that:with the increased of the gate voltage(-2.5 V to 0.5 V),the sensitivity of the sensor decreased,and the maximum sensitivity was obtained at the threshold voltage VG=-2.5 V.When the source-drain voltage was the knee voltage,the sensor sensitivity was maximum.(4)The effects of different temperatures(25-150?)on the response characteristics of AlGaN/GaN HEMT hydrogen sensor were studied.The results showed that:the sensitivity of the sensor decreased as the temperature increased from 25? to 150?,and the hydrogen response characteristics was best at room temperature,indicating that the sensor was suitable for room temperature detection.(5)In addition,the effects of other gases(methane,oxygen)and hydrogen partial pressure on the performance of AlGaN/GaN HEMT hydrogen sensors were investigated.The results showed that:the sensor was less sensitive to methane gas and more selective to hydrogen gas at room temperature.Oxygen could effectively improve the recovery characteristics of the sensor.The sensitivity of the sensor decreased with the decrease of partial pressure of hydrogen.The AlGaN/GaN HEMT hydrogen sensor has excellent response characteristics.It is suitable for room temperature hydrogen detection and has extremely high application potential.