Elias Burstein

The Physics of Semiconductor Materials

Publisher Summary This chapter presents the physics of semiconductors. It discusses chemical binding and energy band structures of semiconductors, lifetime of electron-hole pairs, and impurity and lattice defect center. Sufficient information is now available about the semiconductor properties of a wide variety of materials to understand qualitatively the relations between the semiconductor properties and chemical binding and to indicate trends in the fundamental properties of semiconductor materials. In discussing these relations and trends, however, the chapter is restricted to homologous series of semiconductors with simple structures. These include (1) the group IV-B elements with diamond structures, (2) the M III- B - N V-B , M II-B - N VI-B , and M I-B - N VII-B compounds having the zinc blende or wurtzite structures, (3) the M IV-B - N VI-B , M III-B - N VI-B and the M I-B - N VII-B compounds having the sodium chloride or cesium chloride structures, and (4) the M 2 II-A - N IV-B compounds having the fluorite structure. The chapter discusses forbidden energy gaps and mobilities of materials in the various homologous series of semiconductors with other pertinent physical properties.

The Approximate Determination of Piezoelectric Properties by Measurements on Small Crystals

Procedures for testing and determining the piezoelectric properties of materials by measurements on very small crystals (1‐ to 3‐mm cubes) are described. These include the Giebe‐Scheibe method, the bridge method, and the antiresonance method. A mathematical analysis and an evaluation of these methods are also given. Data obtained from several tiny crystals are compared with data obtained from large specimens.

The photoelastic properties of ionic crystals

Recent photoelastic data are used to obtain values of the change in refractive index with density for a series of cubic crystals. These experimental values are found to be smaller than those calculated from either the Lorentz-Lorenz or the Drude equations. The difference between the experimental and calculated values results from a decrease in the molar polarizability with increase in density. In MgO the change in polarizability is relatively large and the refractive index actually decreases with increase in density while the other crystals show an increase. The decrease in molar polarizability with density as measured by the strain-polarizability, λ0, can be correlated with the amount of homopolar binding and ion overlap in the crystal. It is suggested that an increase in density increases the amount of homopolar binding and ion overlap. Further information about the dynamic changes in polarizability during vibration of the ions can be obtained from the change in refractive index with temperature at constant density and from Raman spectra.