Silicon carbide microwave MESFET´s

Summary form only given. The authors describe record-setting 5-GHz SiC MESFET performance and the effects of device design on achieving these results. Bulk growth of 6H-SiC was performed using a physical vapor transport process, and the resultant undoped single-crystal boules were sliced and polished to generate 1-in-diameter wafers. These wafers were then used as substrates for the chemical vapor deposition of doped silicon carbide active layers. Wafers contained 24 chips, each consisting of an array of MESFETs having systematically varied geometry. A sample DC characteristic from a 320-μm periphery MESFET showed a knee voltage of 8 V, a transconductance of 20 mS/mm, a maximum channel current of 210 mA/mm, and a gate-to-drain breakdown voltage of 100 V. Automated RF probing was used to obtain wafer maps of small signal gain, F_T, and F_max, revealing an excellent transistor yield of 87%. The highest-gain MESFETs in the array developed 12 dB of gain at 2 GHz with a cutoff frequency of 5 GHz