Test And Analysis Of Performance Of Electromechanical Coupling Based On AlGaN/GaN HEMT Micro-cantilever Device

Currently the FET combined with the cantilever structure to achieve theelectromechanical conversion has important applications in Si materials. High electronmobility transistor （HEMT） as one of the field-effect transistor, with its advantages ofhigh-frequency, high-speed, low noise and high-power, has already been widely used in thefield of communications and other fields. HEMT is mostly used as the sensitivity unit of thegas sensor and the RF power sensor. The cantilever beam was processed andelectromechanical coupling mechanism of HEMT micro-cantilever structure was researchedon the basis of ensuring the AlGaN / GaN HEMT epitaxial quality. And it lays a solidfoundation for electromechanical coupling mechanism research manufacturing processingand testing analysis in the field of wide band gap sensors. So the sensitive unit is Si-basedAlGaN / GaN HEMT of the sensor structure designed. AlGaN / GaN HEMT is coupled withthe micro-cantilever structure, so weak mechanical signals through the 2DEG of AlGaN /GaN effected by piezoelectric polarization effects is more sensitive to the electrical response.The article is mainly carried out a systematic study of the testing methods of AlGaN / GaNHEMT sensitive mechanical structure and the electromechanical coupling characteristics.Firstly the output I-V characteristics and the transfer characteristics of AlGaN / GaNHEMT micro-cantilever structure are tested. The results verified that our design of AlGaN /GaN heterojunction high electron mobility transistor structure is reasonable, and provided adata base of designing of testing program to mechanical sensitive structure. According to theelectromechanical coupling principle of AlGaN / GaN HEMT device, a reasonable testingprogram is designed to measure the static characteristics、temperature characteristics andpiezoresistive properties of AlGaN / GaN HEMT micro-cantilever. The mainly items shows as follow：By the detection and analyzing the temperature characteristics of the AlGaN /GaN HEMT, it is found that the current between the drain and source decreased with theincreasing temperature at the same gate voltage. Also, piezoresistive coefficients arecalculated at different temperatures, and the piezoresistive coefficient became lower with thehigher temperature; after detecting the electromechanical characteristics of different workregions for the AlGaN / GaN HEMT, the conclusion that the AlGaN / GaN HEMT owned themost visible electromechanical changes could be got in the saturation region; throughchanges in the current between the drain and source, the difference of piezoelectricpolarization lead by external pressure and the role of the 2DEG concentration in the channelmodulation is analyzed; by detecting the residual stress in material and structure itself, theimpact of residual stress on the performance of device and accelerometer is also analyzed;finally, the equivalent piezoresistive coefficient of the micro-cantilever based on the AlGaN /GaN HEMT was measured and calculated, and its value is（2.47±0.04）×10^-9Pa^-1.The detection results show that the structure of the micro-cantilever is proper, thelinearity is well, and high sensitivity and piezoresistive coefficient are fine. So, all of thisavailably validated the feasibility that the AlGaN/GaN HEMT is designed as the sensitiveunit for force sensing sensor. These study productions make the foundation for further studiesof electromechanical coupling mechanism of AlGaN/GaN HEMT.