High-speed low-voltage ring oscillators based on selectively doped heterojunction transistors

We report ring oscillators which attain high speed at low supply voltage, and thus low power. Selectively doped heterojunction transistors (SDHT´s) were used in a direct-coupled circuit. The GaAs/ Al.3Ga.7As heterostructure, grown by MBE, was designed to allow self-limiting etch of the gate recesses in the driver transistors. Devices with 1 µm gates operated at supply voltages as low as 0.23 V at T = 300 K. At 77 K, gate delays as low as 14.7 ps were observed at 1.0-V bias.