InP-based self-aligned internally series-connected RTD/HBT for threshold gate ICs

An internally series-connected RTD (Resonant Tunneling Diode)/HBT (Heterojunction Bipolar Transistor) technology using an etch back process with a self-aligned base metallization has been proposed. The proposed device shows a reduced peak voltage compared to the externally series-connected device (from 0.88 to 0.77 V). The reduced parasitic resistance values are estimated to be in a range of 10~12 Ω. To demonstrate an applicability of the developed approach to a basic digital gate, a threshold gate has been implemented. At a clock frequency of 3 GHz, the threshold gate IC exhibits the correct performance characteristics.