Ultrahigh-Speed Integrated Circuits Using InP-Based HEMTs

Abstract

The device technologies for 0.1-µm-gate InP-based high electron mobility transistors (HEMTs), which consist of an InAlAs/InGaAs modulation-doped structure on an InP substrate, are described. They yielded a current gain cutoff frequency ( f T ) of over 180 GHz and a transconductance ( g m ) of over 1 S/mm in circuits. An InP recess-etch stopper improved the uniformity of threshold voltage and enabled us to apply HEMTs in digital ICs. A diode consisting of an InAlAs Schottky junction is monolithically integrated with a HEMT and used as a level shifter in digital ICs. By combining novel circuit technologies and the HEMT-IC technologies, the maximum operation speed of IC has been pushed up to over 40 Gbit/s. As a benchmark for future large-capacity networks, electrically multiplexed and demultiplexed 40 Gbit/s, 300 km transmission was successfully demonstrated using the device technologies described here.