Silicon-carbide electroluminescent devices

Abstract
Electroluminescent devices have been constructed from epitaxially grown p-n junctions in silicon carbide. By suitable choice of material polytype and impurities, the luminescence can be controlled, to give various colours covering most of the visible spectrum. Brightnesses in excess of 100ft L (342cd/m2) at current densites of 10A/cm2, have been achieved. The lamps operate at a few volts d.c. and 10–100mA, but pulsed operation at higher currents is possible, and the devices will respond to pulses with rise times below 1µS. Operating lives in excess of 15000h have been obtained at 50mA, with a constant light output. Arrays of lamps fabricated on a single crystal have been found suitable for applying information to photographic film, and as numerical displays. The luminescence intensity of these devices is, generally, proportional to input current, and the area of luminescence remains substantially constant. However, by adding a third electrode to the structure, it is possible to control the area of luminescence of the device with suitable biasing. These devices have applications as magnitude and tuning indicators.

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