Recessed-gate DMTs (doped-channel hetero-MISFETs) with i-AlGaAs/n-GaAs structure and pseudomorphic i-AlGaAs/n-InGaAs/i-GaAs structure have been developed. Broad plateaus in gm and fT provide evidence that the DMTs make the devices suitable for high-speed large-signal operation. GaAs DMTs with 0.35 µm-length have gate turn on voltage of 0.7 V, maximum transconductance of 320 mS/mm and fT of 41 GHz. Pseudomorphic DMTs have gate turn on voltage of 0.9 V, maximum transconductance of 320 mS/mm, fT of 42 GHz and have the enhanced advantages of high current drivability and large gate swing. Further more, with the use of the recessed-gate DMTs, a high-speed laser driver IC for multi-Gb/s optical communication systems are demonstrated. This laser driver IC operates at 10 Gb/s with rise and fall times as fast as 40 psec, and it can drive up to 60 mA into a 25 Ω load.