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This paper describes the motives behind the development of 1.3 & 1.55 pm opto-electronic integrated circuits (OEICs). OElCs for WDM (wavelength division multiplexing) and ATM (asynchronous transfer mode) communications applications are used to explain the materials, design and fabrication issues involved. Factors determining the optimum size of OElCs are outlined.Monolithic integration of transistors revolutionised the electronics industry. It has greatly lowered the cost of devices; controlled parasitics have raised performance, and the enhanced functionality offered by integration allows systems to be built which would have been impractical by integrating discrete devices. Finally, integration has improved reliability.Many of these same forces are driving the monolithic integration of a range of optical components with electronics into an OptoElectronic Integrated Circuit (OEIC). The detailed pressures are, however, different as OElCs will have to compete against hybrid technology in order to become more than a laboratory curiosity.Applications where OElCs are most likely to be a sensible alternative to hybrids are: D fibre-to-the-home systems where whole-life cost minimisation is imperative D element management in communications networks, where the enhanced functionality offered by integrating a mix of components makes hybrids undesirable D high frequency systems, such as radio-fibre, or phased array radar, where control of parasitics is key to a manufacturable process.There is worldwide activity in this field in both industry and academia. This paper will concentrate on development of long wavelength (1.3 & 1.5 pm) OElCs at BT Laboratories because of sapce limitations. Choice Of Devices For QElCsOElCs consist of optical and electronic Ipswich, Suffolk. IP5 7RE UK.components integrated on the same substrate. The need for process compatibility means that the types of device must be carefully chosen if the OEIC is to have good performance. The process must also be chosen to minimise the number of processing stages, to maximise yield. The fabrication sequence is crucial as several high temperature processes may be used. (a) Optical DetectorsIn the work discussed below two types of InGaAs PIN diode have been used: (i) a top-entry PIN diode, with a bandwidth of 20 GHz and a quantum efficiency (QE) of 0.9, (ii) edge-entry PIN diodes with bandwidths up to 50 GHz. Metal-semiconductor-metal diodes (MSM) are another candidate but are not discussed here.(b) Optlcai Emitters Two types of long wavelength laser have been used in this work: (i) ridge Fabry-Perot lasers, which are the simplest type of laser but require cleaved facets to set the operating wavelength.(ii) distributed feedback (DFB) lasers, which are more complex, needing electron-beam lithography to define gratings to set the emission wavelength. They are the preferred device for OEICs. (c) TranslstorsAlthough InP-based transistors can have excellent gain [l], gate-leakage is often high due to materials properties. This limits the transistor types suitable for ...