By building a tiny “cityscape” on a chip of gallium arsenide, with crystal “skyscrapers” less thanone ten-thousandth of an inch high, Cornell University scientists have developed a simple method to improve electronic devices based on gallium arsenide (GaAs). As the basis for high-speed transistors, microprocessors, and tiny solid-state lasers, gallium arsenide outperforms silicon. However, its use has been limited by the number of defects plaguing the sandwich-like devices, in which layers of gallium arsenide with different added elements have been deposited in succession. By building isolated columns of GaAs crystals rather than growing them in large wafers, the traditional way, and then layering them with indium-laced GaAs (lnGaAs), the scientists found far fewer defects. Normally, because lnGaAs crystals are larger, mismatches between them and GaAs layers create defects. This new technique will allow engineers not only to add thicker layers of lnGaAs without increasing defects, but also to increase the...

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