Abstract: A first doped region (20) is grown on a semiconductor substrate (1) as a superlattice region having alternate layers (21, 22) of a first and second semiconductor material followed by a waveguide region (30) having at least a superlattice region with alternate layers (31, 32) of the first and second semiconductor materials. A second doped region (40) is then grown as a superlattice including alternate layers (41, 42) of the first and second semiconductor materials on the waveguide region (30). The first and second doped regions (20 and 40) are grown so that the layers (21, 22, 41, 42) of the first and second semiconductor materials are sufficiently thin and are sufficiently highly doped as to become disordered during growth so that the first and second doped regions (20 and 40) are formed by an alloy of the first and second semiconductor materials having a lower refractive index and larger bandgap than the waveguide superlattice region (30).

Abstract: A method of manufacturing a semiconductor device, in which method a plurality of epitaxial layers are deposited by molecular beam epitaxy. A significant problem in such a method is the variation in the flux emitted by an effusion cell after the shutter associated with that cell has been opened, this resulting in undesired variations in the composition in the thickness direction of the epitaxial layer being grown. In a method according to the invention, when the shutter of a molecular beam source is opened, the rate of input of heat to that source is increased by a predetermined value so that the temperature of that source does not change substantially as a result of the opening of that shutter, and when the shutter is closed the rate of input of heat to that source is reduced by the predetermined value.

Abstract: A method of growing an alloy film by a layer-by-layer process on a substrate is described, together with a method of making an semiconductor device in which an alloy film is grown on a substrate by a layer-by-layer process. The atomic ratio of constituents present in the alloy film is determined during growth of the film from the growth rates of the alloy film and of at least one intermediate film consisting of at least one constituent of the alloy. The intermediate film or films are grown between the alloy film and the substrate. During growth of each film, the growth surface is irradiated with a beam of electrons and measurement is carried out of the period of oscillations in the intensity of the stream of electrons diffracted at the growth surface, or specularly reflected by the growth surface, or emitted from the growth surface, or of the current flowing to ground through the substrate. These periods are equal to the respective times taken to grow on a monolayer of the respective film.