During the last 25 years (after the growth of the first pseudomorphic GeSi strained layers on Si by Erich Kasper in Germany) we have seen a steady accu- mulation of new materials and devices with enhanced performance made pos- sible by strain. 1989-1999 have been very good years for the strained-Iayer- devices. Several breakthroughs were made in the growth and doping technology of strained layers. New devices were fabricated as a results of these break- throughs. Before the advent of strain layer epitaxy short wavelength (violet to green) and mid-IR (2 to 5 f. Lm) regions of the spectrum were not accessi- ble to the photonic devices. Short wavelength Light Emitting Diodes (LEDs) and Laser Diodes (LDs) have now been developed using III-Nitride and II-VI strained layers. Auger recombination increases rapidly as the bandgap narrows and temperature increases. Therefore it was difficult to develop mid-IR (2 to 5 f. Lm range) lasers. The effect of strain in modifying the band-structure and suppressing the Auger recombination has been most spectacular. It is due to the strain mediated band-structure engineering that mid-IR lasers with good per- formance have been fabricated in several laboratories around the world. Many devices based on strained layers have reached the market place. This book de- scribes recent work on the growth, characterization and properties o(compound semiconductors strained layers and devices fabricated using them.

During the last 25 years (after the growth of the first pseudomorphic GeSi strained layers on Si by Erich Kasper in Germany) we have seen a steady accu- mulation of new materials and devices with enhanced performance made pos- sible by strain. 1989-1999 have been very good years for the strained-Iayer- devices. Several breakthroughs were made in the growth and doping technology of strained layers. New devices were fabricated as a results of these break- throughs. Before the advent of strain layer epitaxy short wavelength (violet to green) and mid-IR (2 to 5 f. Lm) regions of the spectrum were not accessi- ble to the photonic devices. Short wavelength Light Emitting Diodes (LEDs) and Laser Diodes (LDs) have now been developed using III-Nitride and II-VI strained layers. Auger recombination increases rapidly as the bandgap narrows and temperature increases. Therefore it was difficult to develop mid-IR (2 to 5 f. Lm range) lasers. The effect of strain in modifying the band-structure and suppressing the Auger recombination has been most spectacular. It is due to the strain mediated band-structure engineering that mid-IR lasers with good per- formance have been fabricated in several laboratories around the world. Many devices based on strained layers have reached the market place. This book de- scribes recent work on the growth, characterization and properties o(compound semiconductors strained layers and devices fabricated using them.

The EC programme on Photovoltaic Power Generation has two distinct parts pilot Projects and R&D contracts on cells, processes, materials, IOOdules and systems. The pilot projects are managed in a totally different w~ fran the R&D contracts. Enphasis ,is put on all aspects of the system such as pcwer conditioning, environmental factors, structures, etc. The aim is to examine all different system aspects, to inprove the performance and the reliability of the overall photovoltaic system and to reduce its cost. A canprehensive overview of the PV pilot programme of the European Gammunities was given in volume 1 of this Series C. R&D contracts, on the other hand, are intended to advance our kn0w- The ledge on all canponents in order to reduce the cost, mainly of the photovoltaic IOOdules. This book reports on the results presented at the sixth contractors' meeting, held about six IlDnths before the end of the current R&D programme.

Amorphous silicon PV panel mass production will require to mas ter plasma chemical deposition in terms of large sizes, cost, maintenance and all other problems related to industrialization. Since plasma deposition is a novel technique, the development of all this production related know how involves a considerable technical research effort. The major problems related to the design of a production deposi tion machine are the following - deposition should be uniform on very large area substrate (typical dimension 1 meter) ; - the deposited amorphous silicon should have good electronic properties (density of state of the order or less than 16 3 10 cm /eV) and very low impurities concentrations (for exam ple oxygen atomic concentration should idealy be less than 0. 01 %) ; - the film stress should be limited, the density of ponctual defects (particulates) should remain reasonable (less than 2 per 100 cm ) ; - dopant level control should be stable and efficient ; - silane consumption should remain reasonably efficient - financial cost being important the machine productivity should be high hence deposition rate optimized ; - downtime due to maintenance should be reduced to a minimum. We present here some results on the R&D effort addressed to the above mentioned problems. An original single chamber was designed. This machine will be made available on the market for R&D purposes by a process machine company. Finally the maintenance problem is considered. Plasma cleaning based on a fluorine containing etchant gases is studied and evaluated. 2.