Characteristic Test Of Micro Accelerometer Based On GaAs-PHEMT Structure

High electron mobility transistor (HEMT) as a field-effect transistor, with advantages of high frequency, high-speed, low noise, high-power advantages, has been widely used in the communications field. Electromechanical coupling of HEMT structure and some relevant researches about micro and nano mechanical sensors based on this structure have attracted international attention in related fields. This structure has been used in gas, liquid, radio frequency and temperature sensors, and good results have been achieved. But there are not many researches which use the HEMT structure as a sensitive element of accelerometers. Pseudomorphic high electron mobility transistor (PHEMT) device has a higher electron mobility, so GaAs-based PHEMT accelerometer as a sensitive element has been designed and fabricated. Many testing have been done about GaAs-based PHEMT accelerometer and the sensitive element PHEMT structure characteristics.Structure and mechanical properties of micro-accelerometer based on GaAs-based PHEMT have been described in this paper. The structure is based on piezoresistive effect of GaAs PHEMT structure. The drain current output of PHEMT changes when the mass receives force. And then the force signal is converted to electrical signal, and the current change is detected through the external testing circuit. This subject is mainly about mechanical properties, I-V characteristics, C-V characteristics, and stability of sensitive element PHEMT structure. And impact factors of drain-source channel current have been analyzed and discussed. The piezoresistive coefficient of GaAs-based PHEMT has been calculated through the three-dimensional turntable testing with value 0.4×10-8pa-1. Secondly, the micro-accelerometer has been calibrated by vibration table test. The dynamical test includes accelerometer sensitivity, linearity and frequency response analysis. Experimental results show that the change of drain current is in according with the static IV characteristic under the dynamic test. The drain current output increases with gate voltage increasing; it increases with the drain voltage in linear region, but remains unchanged in saturation region. The micro-accelerometer has good linearity and sensitivity, and it can be up to 0.177mV / g in saturation region, while the frequency response range is less than 1KHz.By further testing, the micro-accelerometer is designed reasonable and sensitive element PHEMT structure has good mechanical characteristics. The accelerometer has good linearity and relatively stable sensitivity in the low frequency range. This study has laid a foundation for further research about electromechanical coupling characteristics of GaAs-based PHEMT micro structure, and also for optimization of micro-accelerometer structure to get high sensitivity.