Self-sustained acoustoelectric and photoelectric oscillations in systems with relaxation

New acoustoelectric and photoelectric self-sustained oscillation and self-modulation phenomena in systems with relaxation have been investigated. Layered metal-semiconductor-dielectric or piezoelectric structures with external feedback have been studied theoretically and experimentally. The theory presented explains the experimental results and gives a criterion for existence of the phenomena. A quasi-harmonic regime of the self-sustained oscillations is described by the Van-der-Pol equation, which can be very useful for practical applications because it expresses the relaxation properties of the structure in terms of the oscillation frequency. Possible applications of the self-sustained oscillations to new physical and chemical sensors and methods for investigating semiconductors are suggested. Dynamic characteristics of the self-sustained oscillations under different external conditions of as temperature and illumination are discussed