Gallium arsenide depletion MESFET digital integrated circuits

For many years the GaAs MESFET has provided enhanced performance in a wide range of u. h. f. and microwave systems. GaAs digital i.c.s., also using depletion MESFET technology, are now available in research laboratories of many systems companies and commercially. The basic gate delay of ¿ 50 ps provides s.s.i. and m.s.i. functions to exploit the high-speed communications capabilities of optical fibre systems, operating at up to 4 Gbit/s. The main features of the fabrication technology are given for comparison with modern silicon fabrication techniques. Process monitoring for control and device characterization are particularly important to achieve good yield and reproducibility and to minimize the spreads in parameters used for circuit design. High-speed circuit performance depends critically on design and layout and requires careful simulation, including the effects of parasitics and the package. The use of well-characterized `function cells¿ is advocated to reduce the overall design effort and to improve performance predictability.