A NOVEL PROCESSING TECHNIQUE TO FABRICATE PLANAR INGAASP INP ELECTROABSORPTION WAVE-GUIDE MODULATORS/

A novel processing technique has been developed to fabricate planar el ectroabsorption waveguide modulators in compound semiconductor heteros tructures. The lateral confinement of light is achieved by introducing controllable, reproducible, and stable stresses into semiconductor he terostructures using WNi surface stressor stripes, which also serve as electrodes for the waveguide modulators. Self-aligned helium implanta tion is employed to achieve electrical isolation using the stressors a s the templates for the ion masks. An increase as large as 33000 times has been obtained in the de resistance between the neighboring wavegu ide modulators 25 mu m apart. Propagation loss of 1.7 dB/cm is observe d in the photoelastic waveguides at a wavelength of 1.53 mu m followin g the He implantation. A post-implant thermal annealing at 310 degrees C for 40 min increases the de resistance between the neighboring devi ces to the maximum value, and at the same time reduces the optical los s to its value before ion implantation (less than 1 dB/cm). Using a co mbination of the photoelastic effect and helium implantation, planar I nGaAsP/InP Franz-Keldysh-effect waveguide modulators 430 mu m long wit h a 10 dB extinction ratio at 3 V for the TM mode have been fabricated . Planar electroabsorption quantum-confined Stark effect waveguide mod ulators have also been demonstrated. This planar device processing tec hnique may prove valuable in future photonic integrated circuit techno logy.