The Study Of Equivalent Capacitance Of DBRT Structure Affected By Strain

Sensitive component is the main component of a micro-sensor. The design and production of sensitive components depend on the new theories and new materials. The quality of a micro-sensor is largely depends on the performance of its sensitive component. In this thesis, the double-barrier quantum well structure is a model, its equivalent capacitance, which can be affected by strain, is calculated. The relationship between strain and the equivalent capacitance is analyzed, and the concept of meso-piezo-capacitve effect is proposed, which provide a reference for the design of sensitive components.The double barrier resonant tunneling (DBRT) diode composed of super-lattices thin films. External imposition of axial pressure on it will make internal strain which will change the device-geometric dimension of the films, which will change component's tunneling current size, namely the small mechanics signal may have the big electric current change, and many electrical properties of the device will be changed. The research in this thesis focuses on the change of capacity with the pressure, and we call the effect as meso-piezo-capacitve effect.Firstly, start from the resonant tunneling effect of super-lattices, respectively, derives super-lattices tunneling current calculation method and Feimi level calculation method. Some parameters of materials used on the DBRT model are calculated.Secondly, in order to reduce the computational complexity, the DBRT structure equivalent circuit model is made. By calculating the equivalent capacitance ,expression of the model is obtained. The size of the equivalent capacitance and the tunneling current has a close relationship.Finally, the relationship between the material parameters of DBRT model and the strain is calculated, based on knowledge of mechanics of materials. The relationship between strain and the tunneling current is calculated, and the relationship between strain and the equivalent capacitance is calculated too. It is found that when an external bias voltage of the DBRT model is constant, the strain can change the size of the equivalent capacitance, in other words, a force signal can be transformed into a capacitive signal.