11 ps ring oscillators with submicrometre selectively doped heterostructure transistors

Selectively doped AlGaAs/GaAs heterostructure transistor (SDHT) ring oscillators with submicrometre gates have been fabricated using electron beam lithography. Minimum propagation delay of 11.0 ps/gate at 77 K was measured on a 0.4 ¿m gate-length ring oscillator with a power-delay product of 15 fJ at 1.1 V bias. The processing of these structures is described, as well as the testing of the submicrometre transistors and circuits at 300 K and 77 K.