Compound Semiconductors Strained Layers and Devices

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.