Download or read book Optical Properties of Quantum Wells Composed of All-Binary InAs/GaAs Short-Period Superlattices written by Martin D. Dawson and published by . This book was released on 1992 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: Strained alloy InGaAs/GaAs multiple quantum well structures (MQWs), on GaAs substrates, are being investigated' for use in optical modulators, low-threshold diode lasers, photodetectors and other opto-electronic devices operating near 1 um. Attempts are being made to cover the 0.9-1.1 am spectral range by varying well-widths and/or alloy mole-fraction and by growing such structures on superlattice or alloy buffer layers. Special problems, however, are posed in growing these strained ternary alloy quantum wells with high quality by epitaxial techniques. Alloy concentration is difficult to reproduce, and alloy-disorder introduces an additional line-broadening contribution and non-uniformity into the materials. The critical thickness parameter places an upper limit on the indium mole-fraction (and thereby the strain) for growth directly on GaAs, restricting the flexibility in varying the well width for increased spectral coverage. Typically, this mole-fraction must be less than 0.2, and the lattice-parameter mismatch below 2%, for well-widths -10 nm. Here, we focus on structures in which each quantum well consists of an ordered InAs/GaAs short-period superlattice as an attractive alternative to the random InGaAs alloy structures. These all-binary MQWs are highly-strained (7% lattice parameter mismatch) and can accommodate high average indium mole-fraction (30-40%) in wide wells (10-20 nm) without evidence of strain relaxation due to misfit dislocation formation.