Ultrahigh-Frequency Performance of Submicrometer-Gate Ion-Implanted GaAs MESFET’s

Ion-implanted GaAs MESFET’s with gate lengths of 0.3 and 0.5 μm have been fabricated to study the high-frequency performance of short-gate GaAs MESFET’s. Excellent dc and microwave performances have been achieved with an emphasis on the reduction of effective gate length during device fabrication. From f1’s of 83 and 48 GHz for 0.3- and 0.5-μm gate devices, respectively, an electron velocity of 1.5 x 107 cm/s is estimated. An ft of 240 GHz is also projected for a 0.1-μm gate GaAs MESFET. These experimental results are comparable to those of the best HEMT’s reported and higher than those generally accepted for MESFET’s.