Crystalline semiconductor heterostructures

The great advances in solid‐state electronics can be traced to a unique combination of basic conceptual advances, the perfection of new materials and the development of new device principles. Ever since the invention of the transistor at Bell Laboratories almost forty years ago, we have witnessed a spectacular growth in silicon technology, leading to increasingly higher densities of devices and more complex functions. Almost as revolutionary as the invention of the transistor in 1947 was the invention of the laser a decade later. Thus, nearly concurrent with the electronics revolution, we have seen another technological revolution, the so‐called photonics revolution: using beams of laser light for information transmission. The lasers that provide light for today's lightwave communication systems are made not from silicon but from compound semiconductors. These are generally compounds of elements from group III of the periodic table, such as Ga, Al and In, along with elements from group V, most notably As, P and Sb.