GaAs Integrated Logic with Normally-Off MESFETs

Abstract

The normally-off GaAs MESFET digital integrated circuits which feature power dissipation as low as 0.2 mW per gate and sub-nanosecond delay time have been developed. To investigate the power-speed performance of the ICs, ring oscillators with different fan-in/fan-out have been fabricated. For fan-in/fan-out = 1/1 , a propagation delay time is typically 250 ps with a power-delay product of 40 fJ. For fan-in/fan-out = 2/2, the delay time and PD product increase to 430 ps and 97 fJ, respectively. A binary frequency divider with a master-slave flip-flop has been fabricated. Maximum counting frequency was 610 MHz with supply voltage of 1.5 V. Equivalent delay time per gate and PD product are 410 ps and 85 fJ, respectively. By shortening gate length, the operating range of the ICs will be expanded to G bit/s area.