Silicon Germanium CMOS Optoelectronic Switching Device: Bringing Light to Latch

We propose a novel semiconductor optoelectronic (OE) switch that is a fusion of a Ge optical detector and a Si metal-oxide-semiconductor (MOS) field-effect transistor (FET). The device operation principle is investigated, and the performance is explored by simulations. The proof of principle is demonstrated by experiments. The use of Ge enables operation in standard telecommunication wavelengths, in addition to providing the surrounding Si circuitry with noise immunity from signaling. The transconductance of the FET provides amplification, and an experimental current gain of up to 1000 is demonstrated. A complementary function is shown by tailoring the doping profiles. The circuit performance of a complementary pair using the International Technology Roadmap for Semiconductors values for the 150-nm node is evaluated by simulation, yielding ~100-ps cycle times. The switch can be fabricated in the nanoscale regime along with a high-performance Si complementary MOS. A very low capacitance can be achieved due to the isolation of the detection region from the current drive. OE conversion that is performed with such a compact device offers the potential of inserting light at the latch level in a microprocessor.