This book focuses on the theory of phonon interactions in nanoscale structures with particular emphasis on modern electronic and optoelectronic devices. The continuing progress in the fabrication of semiconductor nanostructures with lower dimensional features has led to devices with enhanced functionality and even novel devices with new operating principles. The critical role of phonon effects in such semiconductor devices is well known. There is therefore a great need for a greater awareness and understanding of confined phonon effects. A key goal of this book is to describe tractable models of confined phonons and how these are applied to calculations of basic properties and phenomena of semiconductor heterostructures. The level of presentation is appropriate for undergraduate and graduate students in physics and engineering with some background in quantum mechanics and solid state physics or devices. A basic understanding of electromagnetism and classical acoustics is assumed.

In the presence of an electric field, the dielectric constant of a semiconductor exhibits Franz–Keldysh oscillations (FKO), which can be detected by modulated reflectance. Although it could be a powerful and simple method to study the electric fields/charge distributions in various semiconductor structures, in the past it has proven to be more complex. This is due to nonuniform fields and impurity induced broadening, which reduce the number of detectible Franz–Keldysh oscillations, and introduce uncertainties into the measurement. In 1989, a new structure, surface–undoped–doped (s-i-n+/s-i-p+) was developed, which allows the observation of a large number of FKOs and, hence, permitting accurate determination of electric fields. We present a review of the work on measuring electric fields in semiconductors with a particular emphasis on microstructures using the specialized layer sequence. We first discuss the general theory of modulation techniques dwelling on the approximations and their relevance. The case of uniform field, obtained with this specialized structure as well as that of the nonuniform field, are addressed. The various experimental techniques are also briefly reviewed. We then summarize the various experimental results obtained in the last few years using these special structures and FKOs and find that, even in this short period, good use has been made of the technique and the structure. This is followed by a brief review of the work on nonuniform fields. In this case, the work on actual device structures has significant technological implications. Important issues such as metallization and processing, the effects of surface treatment and thermal annealing, Schottky barrier heights of different metals, piezoelectric fields in (111) grown strained InGaAs/GaAs quantum wells, and Fermi level in low-temperature grown GaAs have been studied using this structure. This structure has also been used to study the dynamics of photomodulation, revealing the nature of the cw photoreflectance.

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