Through-wafer optical communication using monolithic InGaAs-on-Si LEDs and monolithic PtSi-Si Schottky-barrier detectors

Through-wafer optical communication has been demonstrated in experiments employing two vertically stacked Si wafers, the upper one with In/sub 0.15/Ga/sub 0.85/As-In/sub 0.15/Al/sub 0.85/As double-heterostructure LEDs (light-emitting diodes) grown by molecular beam epitaxy on its top surface and the lower one with PtSi-Si Schottky-barrier detectors fabricated on its bottom surface. Infrared radiation emitted by the LEDs in a band peaking at 1.12 mu m, just beyond the Si absorption edge, is transmitted through the upper Si wafer, focused with a 25-mm focal-length lens, transmitted through the lower Si wafer, and detected by the Pt-Si detectors. For a single LED-detector pair, the detector signal-to-noise ratio was 10:1 for an LED drive current, of 1 mA at room temperature. The results suggest that through-wafer communication using LEDs and Schottky-barrier detectors is a promising approach for optical interconnects in stacked wafer architectures.<>