High-transconductance insulating-gate InP/InGaAs buried p-buffer DH-MODFETs grown by MOVPE

Abstract
Buried p-buffer double heterostructure modulation-doped field-effect transistors (BP DH-MODFETs) with an InGaAs quantum-well channel were fabricated with high transconductance and good breakdown voltage, by placing the metal gate directly on Fe-doped InP insulating layer. Excellent extrinsic DC transconductance of 560 mS/mm and a high gate-to-drain diode breakdown voltage (greater than 20 V) were achieved at room temperature with FETs of 1.2- mu m gate length. Unity currently gain cutoff frequency f/sub T/ of 24 GHz and maximum oscillation frequency f/sub max/ of 60 GHz were demonstrated for a drain to source voltage V/sub DS/=4 V, which corresponds to an average electron velocity of 2.2*10/sup 7/ cm/s in the quantum well.