New planarisation process for low current, high-speedInP/InGaAsheterojunction bipolar transistors

Low current, high-speed InP/InGaAs heterojunction bipolar transistors were fabricated using a silicon nitride based planarisation process. Realised devices offered cutoff frequencies of >100 GHz and a DC current gain of >50 at a collector current of only 2 mA. The best maximum frequency of oscillation was 195 GHz. It is also demonstrated that the new planarisation process offers a proper base for the fabrication of integrated circuits. These results increase the competitiveness of InP-based HBTs for high-speed, low power applications.