Sensing and measurement with self-sustained acoustoelectric and photoelectric oscillations in structures with relaxation

The new possibilities of self-sustained oscillations of acoustoelectric and photoelectric voltages accompanied by surface acoustic wave and light self-modulations in layered semiconductor-piezoelectric and metal-dielectric-semiconductor structures with relaxation that we have discovered are presented with a view of sensing of physical and chemical environmental parameters and measurement of semiconductor electronic parameters. It gives principal methods to improve sensitivity and precision because the frequency of the self-sustained oscillation or self-modulation Ω is expressed in terms of the charge-discharge relaxation time τ_s of the metal-piezoelectric-semiconductor or metal-dielectric-semiconductor structures. The frequency of self-sustained oscillations Ω allows relaxation time τ_s to be determined directly. This connection between Ω and τ_s can successfully be used in physical and chemical sensors with frequency output and may be a basis investigations of semiconductor parameters such as surface states´ parameters and their spectroscopy properties. It is the great interest because of in the precise sensors and investigation methods we use self-organization processes in which the frequency of electrical signal can be easily measured with high precision and it gives high sensitivity