A University of Tokyo group led by Professor Mitsuru Takenaka and STMicroelectronics have jointly developed a phototransistor in which a compound semiconductor (InGaAs) is attached to a silicon optical waveguide as an optical absorption layer, demonstrating the highest sensitivity in the waveguide type. By using the silicon waveguide as the gate electrode, extremely weak optical signals (1/trillionth of a watt) were successfully detected. This will facilitate the monitoring of optical signals in silicon optical circuits, and is expected to lead to high-speed control of optical circuits for deep learning and quantum computation. The paper was published in the British scientific journal Nature Communications on December 9.
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