PLASMONS IN TYPES I AND II SEMICONDUCTOR MULTILAYERED FILMS

Abstract

The development of the molecular beam epitaxy technique has increased the interest in the properties of muJtilayered electron gas systems in the past decade. The various aspects of the physics of these semiconductor systems have been studied experimentally and theorectically by many using diverse treatments. We will only focus our attention on the electronic-collective excitation of type I {such as GaAs-AIGaAs} and type II (such as GaSb) heterostructures using coupled Boltzmann equations. These high quality multilayered heterostructures can be grown by MBE. A brief description of the MBE techniques and its applications has been included in the introduction. We also described the epitaxial growth of a GaAs -AIGaAs superlattice. In Chapter 2, we derive the Coulomb potential energies between any two layers for an infinite, semi-infinite superlattice and a finite multilayer using the method of charge imaging. An effective exchange energy in the formalism of Kohn and Sham has also been obtained and added to the direct interaction term to study the effect of exchange on the properties of our system at large wavelengths. In Chapter 3 to 5, we determine the relation between frequency and wavevectors for type 1 multilayered semiconductor films. The bulks, surface and discrete dispersion curves are numerically obtained for a realizable structure of GaAs. The treatment of type I systems are already generalized to type II structures in Chapter 6 to 8. The dispersion relation are found to depend very much on the effective masses of the holes and electrons because of Landau damping. We have shown the dependence by giving three difference examples of electron hole mass combinations. Finally, we included in Appendix E a discussion of the random-phase approximation treatment for a single charge layer and show that it is equivalent to the Boltzmann formalism in the long wavelength limit. Simple electron charge layer