| We have studied issues relevant to the monolithic integration of semiconductor optical preamplifiers with photodetectors for high-speed receiver applications at 1.3 m and 1.55 m. This work stems from the fact that high data-rate optical communication systems have created an increasing demand for sensitive, high-speed optoelectronic receivers at these wavelengths. The approach of optical preamplification is known to increase the ultimate sensitivity possible for a receiver, and the cost of such schemes can often be decreased, with increasing reliability, through monolithic integration.; The study is organized as follows. First, double-heterostructure optical amplifier devices are characterized at 1.55 m for AM modulation-frequency response up to 20 GHz, possibly for the first time. Experimental results include high-frequency effects due to facet reflectivity, as well as low-frequency effects attributed to the carrier-recombination lifetime. Second, a self-aligned processing scheme is developed for fabricating semiconductor lasers, optical amplifiers, and photodetectors in this material system; this scheme emphasizes fabrication simplicity and low contact resistance. In addition, strained-layer and lattice-matched epitaxial structures for optical amplifiers and lasers are developed and grown here, although with limited success. Third, epitaxial layer designs for monolithically integrated amplifiers/photodetectors are proposed and analyzed. Design emphasis is placed on efficient coupling of desired light from the optical amplifier to photodetector, minimization of optical feedback to the amplifier, and reducing the spontaneous emission coupled to the detector. |
