The correlation between inter-modulation distortion of GaAs MESFETs and ungated recess width

Inter-modulation distortion of GaAs MESFET discrete and MMIC PA devices was found to be effected by the width of the ungated recess. Devices with ungated recess width in excess of 105 nm exhibit soft gain compression and out-of-spec inter-modulation performance. Degraded linearity is manifested in worse IM3 and significantly different IM5 dependence on the output power, whereas soft gain compression leads to premature power saturation, smaller power gain and power-added efficiency. Good correlation between the loadpull results, waveform measurements and 2-stage linear power amplifier performance data was obtained. This work provides insight into a critical device parameter for optimum performance of high linearity amplifier applications.