Physics of Thin Films is one of the longest running continuing series in thin film science, consisting of twenty volumes since 1963. The series contains quality studies of the properties of various thinfilms materials and systems.In order to be able to reflect the development of today's science and to cover all modern aspects of thin films, the series, starting with Volume 20, has moved beyond the basic physics of thin films. It now addresses the most important aspects of both inorganic and organic thin films, in both their theoretical as well as technological aspects. Therefore, in order to reflect the modern technology-oriented problems, the title has been slightly modified from Physics of Thin Films to Thin Films.- Discusses the latest research about structure, physics, and infrared photoemissive behavior of heavily doped silicon homojunctions and Ge and GaAs-based alloy junctions- Reviews the current status of SiGe/Si quantum wells for infrared detection- Discusses key developments in the growing research on quantum-well infrared photodetectors (QWIPs)- Reviews Chois development of a family of novel three-terminal, multi-quantum well devices designed to improve high-temperature IR detectivity at long wavelengths- Describes recent studies aimed at using multi-quantum well structures to achieve higher performance in solar cell devices based on materials systems