Researchers marry two semiconductor materials, prepare for terahertz speeds

Two semiconductor materials, both alike in exciting properties, have been combined by researchers and placed on a single wafer to create a chip for applications that have a need for speed.
Written by Jack Clark, Contributor

German researchers have created a semiconductor sandwich of silicon and indium-phosphide to make a chip that, they say, can satisfy the appetites of applications that require dumb-but-fast processing, such as medical imaging or mobile connectivity. 

Scientists from two German scientific institutions - the Berlin-based Ferdinand-Braun-Institut and the IHP-Leibniz-Institut - announced on Tuesday that they have worked out how to combine silicon-based integrated circuits made with the standard CMOS manufacturing process along with indium-phosphide circuits onto the same semiconductor wafer.

"We managed to align both technology worlds so smoothly that the circuits deliver fully the specified high-frequency performance" — Wolfgang Heinrich

The chip, which sees a indium-phosphide circuit placed on top of a silicon-based layer, has the potential to offer higher performance than silicon for certain high-frequency applications. 

"We managed to align both technology worlds so smoothly that the circuits deliver fully the specified high-frequency performance," Wolfgang Heinrich, a professor at the Ferdinand-Braun-Institut, said in a statement (PDF)

Once you go for frequencies above 100GHz on CMOS-based circuits, the output power of the chips falls as the transistor gates find it more difficult to sustain the steady voltages required for the chip's logic to execute.

As a consequence, the scientists have combined silicon with germanium for their chip and paired it with indium-phosphide to make a chip that can be manufactured by the standard CMOS process while also demonstrating performance above typical silicon. 

The scientists' work is still in an early stage and further research has been funded to help them stabilise the manufacturing process and optimise the circuits for mass manufacture.

People have been looking into materials beyond silicon for advanced semiconductors for decades and few of them have met with success. Supercomputer company Cray attempted to create an advanced system based on chips built on Gallium Arsenide (GaAs) in the late 80s through its subsidiary Cray Computer Corporation, but the project suffered from cost overruns and customers went, instead, for the silicon-based chips in the company's Cray C90 systems.

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