Unstrained, modulation-doped, In/sub 0.3/Ga/sub 0.7/As/In/sub 0.29/Al/sub 0.71/As field-effect transistor grown on GaAs substrate

The fabrication, structure, and properties of unstrained modulation-doped, 1- mu m-long and 10- mu m-wide gate, field effect transistors made of In/sub 0.3/Ga/sub 0.7/As/In/sub 0.29/As/sub 0.71/As heterojunctions grown on GaAs substrates using compositionally step-graded buffer layers are described. These devices have a transconductance of 335 mS/mm, f/sub max/ of 56 GHz, and a gate breakdown voltage of 23.5 V.>