Microwave Performance Of Single-gate And Dual-gate Modfets Using Double Hetero'unction Modulation-doped Structures

1.2-/spl mu/m and 0.3-/spl mu/m gate length n+-GaAs/InGaAs/n+-AlGaAs Double Heterojunction Modulation-Doped Field-Effect Transistors (DH-MODFETs)have been fabricated with single and dual controlling gate electrodes. Extrinsic DC transconcluclance of 500 mS/mm has been achieved for a 0.3-/spl mu/m single-gate FET. The device also has an f/sub T/ of 43 GHz and 14 dB Maximum Stable Gain (MSG) at 26 GHz with the stability factor (k) as low as 0.6 from the small signal s-parameter measurements from 0.5 to 26.5 GHz. Dual gate FETs fabricated on the same wafer demonstrate higher gain at low frequencies, but the gain decreases rapidly at high frequencies with the stability factor reaching unity at a rate faster than that single-gate DH-MODFETs. Distinctive power gain roll-off slopes of -3, -6, and -12 dB/octave have been observed forthe dual-gate MODFETs.