Comparison of GaAs device approaches for ultrahigh-speed VLSI

Various GaAs device approaches, their principal attractions, and expected performance levels are discussed in an evaluation of their applicability for ultrahigh-speed VLSI circuits. Relative merits of the approaches are compared to simpler SSI/MSI applications. It is found that while device performance parameters alone, such as current and power gain-bandwidth, may enable the device to be used for ultrahigh-speed or very low power logic, they are not enough for VLSI. Large differences are shown in the inherent sensitivities of the threshold voltage of the device approaches to the vertical and horizontal geometry variations. The GaAs heterojunction bipolar transistor is found to be especially attractive due to its inherent threshold uniformity.