Heterostructure Integrated Circuits based on GaAs or InP technology take advantage of the high-speed high-frequency characteristics of devices such as High-Electron Mobility Transistors, (HEMT's) and Heterojunction Bipolar Transistors (HBT's). A wide spectrum of millimeter-wave and optoelectronic applications can therefore be addressed by recently emerged heterostructure IC technologies. Applications include millimeter-wave front-end receivers consisting of integrated oscillators, mixers and amplifiers and optical receivers with integrated detectors and HEMT or HBT transistor circuits.