Ultrahigh-speed IC technologies using InP-based HEMTs for future optical communication systems

This paper presents the technologies for over-40-Gbit/s operation of InP-ba sed HEMT ICs for future optical communication systems. High-speed interconn ection using low-permittivity benzocyclobutene (BCB) film as an inter-layer insulator decreases interconnection delay and results in highspeed operati on of digital circuits. A static frequency divider and a 2:1 multiplexer us ing this novel interconnection demonstrate 49-GHz and 80-Gbit/s operation, respectively. Ultrahigh-speed digital/analog ICs fabricated using the HEMTs were used in 40 Gbit/s optical transmission experiment and showed good bit -error-rate performance. A novel two-step recess process for gate recess et ching considerably improves the performance of InP-based HEMTs and is found to be promising for future ultrashort-gate devices.