Super low-distortion and high power hetero GaAs MESFETs with asymmetrical LDD structure

We have developed hetero GaAs MESFET with an asymmetrical Lightly Doped Drain (LDD) structure to improve the IM3 for base station applications of digital wireless systems. The IM3 at the high and low back-off region was improved simultaneously by optimizing an LDD region. The key points to improve the IM3 are suppressing the impact ionization phenomenon, increasing the gate-drain breakdown voltage and decreasing the on-resistance. The IP3 of 60.5 dBm at high back-off was obtained for 10 W-class FET in class-A operation. A Linearity Figure-of-Merit (L.F.O.M.) of 70.1 was recorded. The PAE of 39.5% at the IM3 of -35 dBc (at low back-off) was obtained for 20 W push-pull FET in class-AB operation.