Theoretical Approach to Polarization Effects in Semiconductors

As a rule, investigations of physical effects in solids are motivated by the need of understanding at a fundamental level, which facilitates their effective application in the fabrication of devices. The problem of electrical polarization of piezoelectric, ferroelectric, and pyroelectric solids is no exception. In the last 15 years we have witnessed very intensive investigations of the theory of spontaneous polarization, as well as of the dielectric response of crystals to external perturbations. Our current understanding stems from the development of electronic structure calculations based on first principles, and subsequently from evolution of appropriate theoretical approaches allowing for both a proper definition of polarization and accurate calculations. From the experimental side, much of the impetus came from experimental work devoted to, e.g., GaN-like group-III nitrides, in which internal electric fields of both pyro- and piezoelectric origin are large, determining the properties of quantum structures and devices [1]. Spectacular progress in this area has led to innovative devices described in several chapters of this book.