Results on gate-length scaling of the performance of enhancement-mode heterostructure field-effect transistors (HFET's) for gate lengths between 0.4 and 10 μm, are reported. The devices studied were fabricated by a self-aligned gate process. Transconductances as large as 534 mS/mm were achieved with 0.4-μm, devices. We compare two types of pseudomorphic AlGaAs/InGaAs/GaAs heterostructures. One of them is used for modulation-doped FET's and the other for doped-channel FET's. We find that the effects of electron velocity saturation are different for the two types of devices due to the dominance of charge transfer and gate leakage in the conventional modulation-doped device. The experimental results are explained in the framework of a simple charge control model.
Bibliographical noteFunding Information:
Manuscript received July 31, 1989; revised October 17, 1989. This work was supported by Air Force Contract F33615-86-C-1128 monitored by M. Curtis of Wright-Patterson Air Force Base. The review of this paper was arranged by Associate Editor S.-S. Pei.