Mobility profiling of GaAs power FET´s by magnetotransconductance measurements

Mobility profiles of GaAs power MESFET´s have been measured using the magnetotransconductance technique. Unlike devices with small gate widths, large periphery power devices exhibit significant parasitic resistance effects, and corrections have to be made. To obtain a realistic mobility profile of the channel, precise measurement of the magnetic field dependence of the transconductance and parasitic resistance is necessary. The technique for obtaining these accurate measurements is detailed. The FET´s studied are standard microwave power devices for amplifier circuit applications. Devices having gate peripheries of up to 3.5 mm have been studied, and corrected mobility in the range of 3500-6000 cm²/V . s has been obtained.