The mid-infrared (2-10µm) spectral region is of enormous scientific and technological interest because it contains the strongest fingerprint absorption bands of a number of pollutant and toxic gases which require monitoring in a variety of different situations (e.g., oil-rigs, coal mines, landfill sites and car exhausts) and in concentrations, ranging from parts per billion to almost 100%. Organic liquids, narcotics and many biological and bio-medical analytes also have fingerprint absorptions in this spectral range. In addition, the atmospheric transmission window between 3 µm and 5 µm enables free-space optical communications, thermal imaging and the development of infrared counter-measures for "homeland security". However, many of these applications require technology based on un-cooled, efficient, inexpensive sources and detectors which are not yet available and so wide exploitation of this spectral range has yet to take place.

There is no doubt that the practical realisation of mid-infrared semiconductor lasers, LEDs and detectors which can operate at room temperature will transform them from a specialist research curiosity to a pervasive technology that will unlock a wide variety of applications. Many of the necessary developments depend on the ability to fabricate suitable high-quality epitaxial materials through the use of strained-layer engineering at the nanoscale and to manipulate the optoelectronic properties of the corresponding quantum device structures. There are a number of different materials, active region designs and device structures currently being investigated for both light sources and detectors. Many of the salient features together with recent progress in each of these areas is presented in this text.

Mid-infrared Semiconductor Optoelectronics is an overview of the current status and technological advances in this rapidly developing area. It is divided into four parts. First, some of the basic physics and the main problems facing the device engineer (together with a comparison of possible solutions) are presented. Next, there is a consideration of the different types of lasers currently under development. For practical mid-infrared applications semiconductor lasers must operate at room temperature and several different approaches to achieve this, particularly within the difficult 3-4 µm spectral region are discussed. Part III reviews recent work on light-emitting diodes and photodetectors and also deals with negative luminescence. The final part of the book is concerned with applications and highlights, once more, the diversity and technological importance of the mid-infrared spectral region.

The text has been produced by a world-wide authorship of experts in mid-infrared physics and technology, each working at the cutting edge in their own specialist area. Mid-infrared Semiconductor Optoelectronics will be an invaluable reference for researchers and graduate students drawn from backgrounds in physics, electronic and electrical engineering and materials science. Its breadth and thoroughness also make it an excellent starting point for further research and investigation.

Professor Anthony Krier is the head of the Condensed Matter Division of the Physics Department at Lancaster University, UK. His research is in the optoelectronic properties of semiconductor and polymer materials and the fabrication of diode and laser devices emitting in the 2-10 µm (mid-infrared) range. He is the co-ordinator of the Mid-infrared Network. This EPSRC (UK's Engineering and Physical Sciences Research Council) network has been created to bring together expertise and facilitate research in key areas of semiconductor materials growth, device physics and fabrication in order to advance the technology of mid-infrared optoelectronics. The network links centres of excellence throughout the UK and Europe. This book represents a collaboration between many of these labs which has been substantially supplemented (nearly 50% of the text) by contributions from leading American researchers in this field.