High-speed InP/InGaAs heterojunction phototransistor for millimetre-wave fibre radio communications

Abstract

We report on the performance of a graded-base InP/InGaAs heterojunction phototransistor (HPT) as a direct photodetector and an optoelectronic up-converter in 30 GHz band, investigated at a wavelength of 1.55 /spl mu/m. HPT performances were improved according to the optimised base contact design in order to obtain a higher optical gain G/sub opt/ up to the millimetre-wave range. It is also shown, by analysis and measurements, that a complete description of HPTs can be made using a three-port network representation, with the optical window as an input port. This approach has several advantages in particular, the extraction of the 'optical' transducer power gain G/sub OT/ of the HPTs, needed for designing optoelectronic integrated circuits, OEIC.