High-performance GaAs MESFETs with advanced LDD structure for digital, analog, and microwave applications

GaAs MESFETs with advanced LDD structure have been developed by using a single resist-layered dummy gate (SRD) process. The advanced LDD structure suppresses the short channel effects, and reduces source resistance, while maintaining a moderate breakdown voltage. The 0.3-μm enhancement-mode devices exhibit a transconductance of 420 mS/mm, while the breakdown voltage of the depletion-mode device (V_th=-500 mV) is larger than 6 V. The standard deviation of the threshold voltage for 0.3-μm devices is less than 30 mV across a 3-in wafer. The 0.3-μm devices exhibit an average cutoff frequency of 47.2 GHz with a standard deviation of 1.3 GHz across a 3-in wafer. The cutoff frequency of a 0.15-μm device is as high as 72 GHz. D-type flip-flop circuits for digital IC applications and preamplifier for analog IC applications fabricated with 0.3-μm gate length devices operate above 10 Gb/s. In addition, the 0.3-μm devices also show good noise performance with a noise figure of 1.1 dB with associated gain of 6.5 dB at 18 GHz. These results demonstrate that GaAs MESFETs with an advanced LDD structure are quite suitable for digital, analog, microwave, and hybrid IC applications