Using a self-aligned base contact process and proton implantation to reduce extrinsic base-collector capacitance, we have improved the high-speed performance of AlGaAs/ GaAs heterojunction bipolar transistor digital circuits. The cutoff frequency of the transistor fT with an emitter width of 2 0 μm is 45 GHz. NTL ring oscillators have operated at 16-5 ps/gate and CML ring oscillators at 27.6 ps/gate. Frequency dividers (1/4) have operated up to 11 GHz with wafer-probe testing. These are record speeds for bipolar circuits.
- Digital circuits
- Semiconductor devices and materials