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After Silicon
Microprocessors made of a different semiconductor

Source: “Beyond CMOS: Logic Suitability of In0.7Ga0.3As HEMT”
D. H. Kim and J. A. del Alamo
Paper presented at the International Conference on Compound Semiconductor Manufacturing Technology, April 24-27, 2006, Vancouver, British Columbia

Results: MIT researchers have made a transistor out of a nonsilicon semiconductor that, in early stages of development, provides speed and performance similar to those of state-of-the-art silicon transistors while consuming less power.

Why it matters: The properties of compound semiconductors such as indium gallium arsenide or indium antimonide make them attractive alternatives to silicon. Electrons move through compound semiconductors as much as 50 times faster than they do through silicon; compound-semiconductor transistors thus operate at a lower voltage, consume less power, and produce less heat that can damage a chip.

The excellent optical properties of compound semiconductors could offer another advantage. Since compound semiconductors easily produce light, photons could potentially zip data between transistors without copper wires.

Methods: The researchers used a common deposition process to build up layers of indium gallium arsenide and of the insulating material indium aluminum arsenide – the “gate dielectric” that prevents electron leakage between the transistor and its “gate,” which turns it on and off. They then used an electron beam to carve out the gate. Finally, the researchers added the metal contacts – made of nickel, germanium, and gold – that are used to put electrons in and take them out of the transistor.

Next Steps: With silicon transistors, the gate dielectric, which is made of an insulator called silicon dioxide, grows on top of the silicon when it is exposed to oxygen. Compound semiconductors, however, have poor interfaces with their oxides. The researchers are conducting tests to determine which gate dielectric material will optimize the performance of their transistors.

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Tagged: Computing

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