Semiconductor Lasers

Although the growth of lattice-matched layers is very important for the fabrication of reliable semiconductor lasers, it is possible to fabricate high-quality semiconductor lasers using materials with a small degree of lattice mismatch among them. sup 98-100 This lattice mismatch introduces strain on the layers, altering the semiconductor band structure. Typical values of strain (delta/a, where a is the lattice constant of the substrate and delta is the difference in lattice constants between the substrate and the epitaxial layer) are less than 1. 5 percent. The larger the amount of strain, the thinner is the layer that can be grown free of dislocation on the substrate. Beyond a certain thickness, known as the critical thickness, sup 101 very large number of dislocations are generated, and the luminescence properties of the material become quite poor.