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

This paper presents the technologies for ovcr40-Gbit/s operation of InP-bascd HEMT ICs for future optical communication systems. High-speed interconnection using low-permittivity benzocyclobutene (BOB) film as an inter-layer insulator decreases interconnection delay and results in highspeed operation of digital circuits. A static frequency divider and a 2:1 multiplexer using this novel interconnection demonstrate 49-GHz and 80-Gbit/s operation, respectively. Ultrahighspeed digital/analog ICs fabricated using the HEMTs were used in 40 Gbit/s optical transmission experiment and showed good bit-crror-rate performance. A novel two-step recess process for gate recess etching considerably improves the performance of InPbased HEMTs and is found to be promising for future ultrashortgate devices.