Design And Characteristic Measurement On A Meso-Piezoresistance Accelerometer

With the rapid development of MBE (Molecular Beam Epitaxy) and NEMS (Nano-Electromechanical System) fabrication technology, various superlattice quantum well devices have been fabricated today. When the critical dimension of device approaches nanometer magnitude, several effects will be appeared including the quantum effect. So, these novel devices will appear new characteristics and good performances, because of the dimensional effect. In this thesis, we study the Meso-piezoresistance Effect based on GaAs superlattice semiconductor thin films. The Meso-piezoresistance Effect can be defined as following: Once a mechanical signal is applied for the resonant tunneling heterostructure (RTH), the RTH will experience the induced strain, which will come into being the built-in electric field in the thin films. The strain and built-in electric field will lead to the change of electronic energy states (such as a shift), which will influence on the value of the tunneling current. Thus, a weak mechanical signal can be converted into a strong tunneling current signal in principle through the four physical processes stated above.In this thesis, we have designed and fabricated AlAs/InGaAs/GaAs double-barrier resonant tunneling thin films based on the theory of Meso-Piezoresistance Effect. The different dimensions of accelerometer have been design and analyzed by the software MATLAB. Meanwhile, the accelerometer has been simulated by ANSYS9.0 software. To decrease the parasitic capacitance and control the thickness of the cantilever accurately, RTH and cantilever are successfully fabricated by air-bridge and control hole technique separately.The Raman spectrum system has been introduced as the quantitative analysis of the external pressure on RTH in the static experiment, and dynamic experiment has conducted on the accelerometer by the electromagnetic platform vibrator measurement system. The measurement results show that the dynamic sensitivity of the accelerometer can be changed by changing the bias voltage, and the sensitivity in the negative difference resistance region is much higher than that in the positive difference resistance region. Moreover, the maximum dynamic sensitivity appears at the point of valley voltage, which is accordance with the measured results of static piezoresistive sensitivity characteristic.This thesis brings forward the main innovation spot as following:b) Breaking through the traditional Electro-mechanical coupling laws, the accelerometer is designed based on the Meso-piezoresistance Effect of resonant tunneling heterostructure, which is integrated on the cantilever as the sensing element.a) The air-bridge technique has been developed, and double air-bridge resonant tunneling heterostructures have been successfully fabricated by the technique.c) The static piezoresistive sensitivity can be adjusted by changing the bias voltage on resonant tunneling heterostructure and the measured maximum appear at the point of valley voltage, which is promise one order higher than Si piezoresistive device.