Applied Physics

New Jobs for Nitrides

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Science  19 May 2000:
Vol. 288, Issue 5469, pp. 1137
DOI: 10.1126/science.288.5469.1137b

Thin films of GaN and related nitride semiconductors have found use in light-emitting and laser diodes, and other applications for these materials are being pursued. For example, Schottky-barrier photodetectors based on AlGaN films grown on sapphire show promise as detectors of harmful solar ultraviolet radiation. The growth of these films on silicon substrates would offer several advantages, including lower cost and easier device integration, but devices grown on Si have had slower response times and unwanted sensitivity to visible light, in part because of interdiffusion.

Pau et al. used plasma-assisted molecular beam epitaxy to grow Si-doped AlGaN films on Si(111) surfaces with intermediate layers of Al and AlN. These devices show comparable performance to those grown on sapphire. The InGaAsN family of materials has applications in long-wavelength lasers and solar cells. Chang et al. show that the lower band gap of this material makes it an excellent candidate for low-power P-n-p heterojunction bipolar transistors (HBTs) with AlGaAs. The transistors exhibit a peak current gain of 23 and have a turn-on voltage of 0.77 volts, a quarter volt lower than comparable AlGaAs/GaAs HBTs.—PDS

Appl. Phys. Lett.76, 2785 (2000); Appl. Phys. Lett.76, 2788 (2000).

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