Abstract

We have observed low-loss waveguiding at λ = 1.3μm in a thin 0.15μm layer of Ge_xSi_1−x sandwiched between a 2μm Si capping layer and a silicon substrate (the first waveguide of its kind, to our knowledge). Germanium concentrations of 8–18% were tested, and the low-defect GeSi alloy film was grown by chemical vapor deposition at 1000°C. Electron diffraction microscopy revealed that the GeSi is coherently strained with 1% lattice dilation normal to the Si layer and that there is no distortion parallel to the layer. Previous waveguiding work¹ focused on an air-clad GeSi layer that was several microns thick. The current experiments suggest that a submicron GeSi base layer will support infrared waveguiding within an elongated Si/GeSi/Si heterojunction bipolar transistor (HBT). The long-range goal of this work is to demonstrate that an npn or pnp channel-waveguided Si/GeSi/Si HBT will provide ultrafast optical intensity or phase modulation by carrier injection into the base.

© 1990 Optical Society of America