Methane Gas Sensor Based On GaN Nanowire

Methane is the simplest hydrocarbon in nature.It is also a ma jor component of natural gas.As an efficient and reliable energy source,methane has been widely used in industrial and domestic fields.However,when the concentration of methane in the air is in explosion limit range,it is prone to cause explosion which can bring heavy casualties and property losses.Methane is colorless and odorless and non-toxic so it is difficult to detect by traditional means.Therefore,the development of a reliable and highly sensitive methane gas sensor has important application value.At present,semiconductor materials are most widely used in the field of gas sensing due to their good photoelectric properties,high sensitivity and easy integration.Compared with other semiconductor materials,gallium nitride is a third generatio n semiconductor with wide band gap(3.4V)and better chemical stability(difficult to be corroded by strong acid).It is a hot spot in semiconductor research all over the world and has a board application prospect in high-frequency,high-power device.As the core device of Internet of things,sensors must continuously improve a serious of indicators such as sensitivity,response speed and stability in order to meet the requirement of practical application.Based on the fabrication of direct bridge growth of GaN nanowires,this paper conduct research on its application in methane gas sensing.Research content mainly includes the following aspects:(1)A bridge nanowires array growing vertically to the channel was prepared by means of MOCVD.The surface of GaN nanowires was decorated with different kind and thickness of noble metal by magnetron sputtering.By means of SEM,XRD and other characterization methods,the morphology,structure,and crystal quality of the material were analyzed.(2)Detailed methane gas test was carried out at room temperature.By comparing the test results,it was found that Pd had the greatest improvement in methane sensing.The detect limit of the obtained 10 nm Pd decorated GaN nanowire sensor to methane is as low as 20 ppm.Moreover,it has good repeatability and stability.(3)The photoelectric response of nanowire devices and the influence of ultraviolet light on the gas sensitivity of Pd-GaN nanowire were tested.Under the condition of 365 nm ultraviolet light,the methane measurement index was improved,and the response time was as low as 4 seconds in the low concentration range.(4)The gas sensing mechanism is studied and explained and the effects of Pd modification and ultraviolet irradiation were discussed.