Abstract: A phototransistor which is capable of operating alternately in the emission mode and in the reception mode can be coupled under favorable conditions to an optical fiber in a telecommunications system. An active layer constitutes the base of the transistor and forms a heterojunction with two layers of opposite conductivity type which constitute the emitter and collector of the transistor. The base contact is formed by a heavily doped region of the same conductivity type as the active layer and defines the useful zone of photon coupling between the optoelectronic component and the entrance face or exit face of the optical fiber.

Abstract: A phototransistor in planar technology for optical fiber communications permitting an easy formation of the contact connection of the transistor base located within the intermediate layer of an npn stack as well as accurate localization of the pn junction. To this end, the upper semiconductor layer initially receives a first diffusion of doping impurity in a first region which penetrates into the lower layer to a slight extent and forms the base region. An impurity of opposite type is then implanted in a second region which is located within the first and forms the emitter region whilst the substrate constitutes the collector. The base and emitter connections are formed on the free face whilst the collector is connected on the substrate side.

Abstract: The invention relates to a low cost photovoltaic cell, using a minimum thickness layer of semiconductor compounds able to provide the photovoltaic effect and specifically in polycrystalline form. On a molybdenum sheet an auxiliary polycrystalline germanium layer is deposited in order to facilitate subsequent depositions. This is followed by an intermediate polycrystalline layer of gallium aluminum arsenide and an active layer of polycrystalline gallium arsenide. The presence of the intermediate layer with a wider forbidden band than that of the active layer compensates the effect on the efficiency of the limited thickness of the active layer.