GAAS INTEGRATED OPTICAL CIRCUITS BY WET CHEMICAL ETCHING

An integrated optical circuit containing a laser, passive waveguide, and extra-cavity detector is described. These devices are fabricated from AlxGa1-xAs layers grown by liquid-phase epitaxy. Reflectors are formed by a two-step preferential etch procedure. For proper laser orientation on {100} wafers, the mirrors are found to be oblique, tapered so as to enhance coupling into the underlying passive waveguide; this increases the efficiency of radiation transfer to the detector. Device operation with high differential transfer efficiency and low threshold has been achieved; e.g., for devices with one etched mirror and one cleaved mirror, nt= 16 percent and Jt= 2.4 kA/cm2, whereas these values are nt = 6.5 percent and Jt = 3.0 kA/cm2 for devices with two etched mirrors. Other orientations on {100} and {100} wafers have also been investigated. The reflectivity of the etched mirrors is small, Re ≃ 1–2 percent, but transfer efficiencies into the external passive waveguide as large as T = 50 percent have been observed. The effect of small Re on device performance is examined both experimentally and theoretically. The fabrication of ribbed interconnections between active circuit components is also described. Copyright © 1979 by The Institute of Electrical and Electronics Engineers, Inc.