High-performance double-modulation-doped InAlAs/InGaAs/InAs HFET's

We demonstrate the improvement of double-sideddoped InAlAs/InGaAs MODFET's by inserting a thin InAs layer in the center of the conventional InGaAs channel. A maximum extrinsic transconductance of 1.4 S/mm is achieved for 0.13-μm devices. The current gain cutoff frequency of this device is as high as 265 GHz. Delay time analysis shows a significant improvement in the effective saturated velocity, from 2.4 × 10⁷ cm/s for LM devices to 3.1 × 10⁷ cm/s for InAs devices. We believe the superior performance of this device is primarily due to the reduction of scattering from donor layers, especially under the channel, and the interface roughness, which is achieved by inserting a 4-nm InAs layer in the channel.