On-chip electrical global interconnection will become a bottleneck as CMOS scaling continues. Optical waveguides offer a viable solution to the imminent global interconnect problem in CMOS ICs [1]. The technology for bringing opto-devices into CMOS is the key issue for intra-chip optical interconnection. We have demonstrated the assembly of the thin-film Vertical Cavity Surface Emitting Laser (VCSEL) and the thin-film photodetector (PD) onto CMOS ICs before [2][3]. This is the first report, to our knowledge, of the intra-chip optical interconnection with an optical waveguide and heterogeneous integrated III-V opto-devices in a CMOS IC. VCSELs and PDs were fabricated on respective GaAs wafers and lifted off the wafers using epitaxial liftoff technique with an AlAs sacrificial layer [4]. These devices have a tile like appearance and adhere to handling plastic tape with a feeble adhesive. The size of the thin-film VCSEL and PD are 7×100×200μm and 2×120×120μm respectively. Our VCSEL is an 850nm-wavelength top-emitting type with a triple GaAs quantum wells and an oxide current aperture. Both anode and cathode electrodes are formed on the top surface of the film. The thin-film PD is an inverted metal semiconductor metal (I-MSM) type, which has finger electrodes on the bottom of absorbing layer to avoid shadowing loss [5]. The inverted MSM consists of an i-GaAs absorbing layer with an i-Al{sub}0.2Ga{sub}0.8As barrier layer, a pair of finger patterned Schottky electrodes, and connecting electrodes on a polyimide pedestal. The size of detecting area is 75×75μm{sup}2.
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