Metal Organic Vapour Phase Epitaxy for the Growth of Semiconductor Structures and Strained Layers

Abstract

The technological development of semiconductor materials started in the period following the second world war. In the electronics industry, the first transistors were fabricated from germanium, later from silicon. It was soon realized that also the A^III–B^V or A^II – B^VI materials (most often simply termed III–V or II–VI materials) exhibited semiconductive behaviour. The energy difference between the valence band and the conduction band made them candidates for electronic devices which can absorb or emit phonons over a range of frequencies (wavelengths). Direct bandgap materials such as gallium arsenide (GaAs) were suitable for devices in which efficient electron-hole recombinations could take place and high efficiency light emitting devices were a possibility. Stimulated emission was first demonstrated in 1970 with the preparation of the single heterojunction and the double heterojunction laser diodes. These devices are multiple layer structures with a thin waveguide region contained between layers of larger bandgap and different refractive index (for confinement of carriers and radiation, respectively, in the active region). A basic laser diode chip consists of two parallel facets, (110) planes, which are prepared by cleavage and act as mirrors. The Fabry-Perot cavity is defined by these two parallel facets and the passive (cladding) layers. In the longitudinal direction current definition is by mesa etching and/or stripe-contact metallization.