Research On Properties Of AlGaN/GaN High Electron Mobility Transistor Temperature Sensor

Semiconductor temperature sensors have the advantages of high sensitivity,small size,low power consumption and strong anti-interference ability.They have been widely used in medical,industrial,aviation and civil fields.However,most temperature sensors based on silicon are not suitable for use in high temperature environments.The new AlGaN / GaN heterojunction material not only has a wide band gap,but also has a high two-dimensional electron gas concentration and carrier mobility.Therefore,the devices made with it can not only be used in ultra-high temperature environments,but also have good electrical properties.Based on the above background,this paper studies the fabrication process and device characteristics of AlGaN / GaN high electron mobility transistor(HEMT)temperature sensor devices.The fabrication process of AlGaN / GaN HEMT millimeter-scale large-scale devices was studied using semiconductor technology,mainly including the preparation of device ohmic contacts and the study of lithography.Experiments show that at 830?,ohmic contact can be obtained by annealing in a nitrogen atmosphere for 50 s.The photolithography experiment showed that after 40 s exposure and 50 s development,the pattern can be developed clearly and neatly.At this time,the photoresist denaturation time is more appropriate,and the pattern can be clearly presented through proper development.When the reversal baking temperature is 85?,the graphics can be reversed well,and the graphics can be clearly presented,and the edges are relatively smooth.The variable-temperature output characteristics of the millimeter-scale gateless AlGaN/ GaN HEMT temperature sensor were tested.Experiments show that the change of the voltage across the device with temperature at a fixed current of 0.01 A can be well fitted with the E index model,which is consistent with the theoretical analysis results.The sensitivity can reach 44.5mV/? when the device size is 6.1mm × 0.8mm.Changing the channel length L of the device can adjust the sensitivity of the device,and the sensitivity will increase as L increases.Tests on AlGaN / GaN HEMT devices with a channel length of several hundred micrometers show that the average sensitivity of the small-size devices with an electrode spacing of 246?m at 0.01 A across the voltage drop with temperature changes to 30.4mV/?.It can be seen from the variation curve of device sensitivity with electrode spacing that when the electrode spacing increases,the device sensitivity will increase by substantially the same multiple.In this paper,the device stability of AlGaN /GaN HEMT temperature sensor is also studied.The changes in electrical characteristics of the device before and after constant temperature maintenance and constant temperature energization maintenance were measured.Constant temperature stability experiments show that the electrical characteristics do not change much after the device is exposed to high-temperature air or nitrogen atmosphere at 300,400,and 500? for a long time,and it has good high-temperature stability.In addition to the device's high temperature stability,the device's high temperature operating stability experiment shows that the voltage signal will not change within 2 hours when the device is operating below 500?,and the voltage fluctuation is within 1%.High temperature working stability.But when the operating temperature of the device reaches 600?,the voltage signal gradually increases with time.From the linear fitting of the ± 1V interval of the variable temperature I-V characteristic curve of the transmission line model,the relationship between the total resistance of the device and the electrode spacing can be obtained.It can be seen that the contact resistance and specific contact resistivity of the device do not change much before 400?,and the contact resistance basically changes in the range of 2? to 5?,but suddenly increases at 500?.