Comparisons of microwave performance between single-gate and dual-gate MODFETs

Both a 1.2- mu m and a 0.3- mu m gate length, n/sup +/-GaAs/InGa/n/sup +/-AlGaAs double-heterojunction MODFET have been fabricated with single-gate and dual-gate control electrodes. Extrinsic DC transconductance of 500 mS/mm has been achieved from a 0.3- mu m single-gate MODFET. The device also has a current gain cutoff frequency f/sub T/ of 43 GHz and 14-dB maximum stable gain at 26 GHz with the stability factor k as low as 0.6 from the microwave S-parameter measurements. At low-frequency dual-gate MODFETs demonstrate higher gain than the single-gate MODFETs. However, the k of dual-gate MODFETs approaches unity at a faster rate. Power gain roll-off slopes of 3-, 6-, and 12-dB/octave have been observed for the dual-gate MODFETs. >