Browse Prior Art Database

Light Emitting Diode

IP.com Disclosure Number: IPCOM000074393D
Original Publication Date: 1971-Apr-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 3 page(s) / 31K

Publishing Venue

IBM

Related People

Shang, DC: AUTHOR

Abstract

Light-emitting diode (LED) 10 of A has multiple discrete emission wavelength characteristics. LED 10 is of the GaTlP type. At room temperature, i.e., 27'C, it has a normal current versus voltage characteristic indicated by the dash line continuous curve of B. At room temperature, when LED 10 is biased in the forward direction at a voltage sufficient to emit light, its wavelength emission characteristic is approximately 6300 angstroms. It does not emit light at room temperature when biased in the reverse direction.

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Light Emitting Diode

Light-emitting diode (LED) 10 of A has multiple discrete emission wavelength characteristics. LED 10 is of the GaTlP type. At room temperature, i.e., 27'C, it has a normal current versus voltage characteristic indicated by the dash line continuous curve of B. At room temperature, when LED 10 is biased in the forward direction at a voltage sufficient to emit light, its wavelength emission characteristic is approximately 6300 angstroms. It does not emit light at room temperature when biased in the reverse direction.

At -196 degrees C, LED 10 exhibits a current versus voltage characteristic indicated by the solid line discontinuous curve of B. To subject the LED to this temperature, it may be placed in a liquid nitrogen atmosphere. Under these temperature conditions, increasing the voltage in the forward direction will cause the LED to emit light at 6300 angstroms when the voltage reaches V2, which is typically 20 volts, c.f. discontinuous curve portion If. The LED continues to emit light at this wavelength until the voltage V3, which is typically 30 volts, is reached. At V3, the LED "breaks down" and the voltage across it drops to V1, which is typically around 12 volts, c.f. discontinuous curve IIf. Moreover, the LED now emits a different wavelength of 5700 angstroms. If the voltage is thereafter increased in the forward direction, the LED continues to emit at 5700 angstroms, but the voltage across the LED becomes rapidly saturated in this direction, c.f. curve portion IIf. If the voltage is lowered in the reverse direction, the LED stops emitting when the voltage level drops below VI. Thereafter, if the volt is increased in the forward direction and passes VI, the diode will not emit light until it reaches V2 whereupon it again emits light at 6300 angstroms. The afore- described operating cycle must be repeated if it is desired to have it emit at 5700 angstroms. That is to say, if the diode is emitting at 5700 angstroms and is subsequently turned off, it must first be operated in the curve If portion of its characteristic to its "breakdown l...