Ultraviolet light emitting diode

Abstract

A light emitting diode is disclosed. The diode includes a silicon carbide substrate having a first conductivity type, a first gallium nitride layer above the SiC substrate having the same conductivity type as the substrate, a superlattice on the GaN layer formed of a plurality of repeating sets of alternating layers selected from among GaN, InGaN, and AlInGaN, a second GaN layer on the superlattice having the same conductivity type as the first GaN layer, a multiple quantum well on the second GaN layer, a third GaN layer on the multiple quantum well, a contact structure on the third GaN layer having the opposite conductivity type from the substrate and the first GaN layer, an ohmic contact to the SiC substrate, and an ohmic contact to the contact structure.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application is a divisional of copending U.S. application Ser. No. 10 / 170,577, filed Jun. 12, 2002 now U.S. Pat. No. 6,664,560.FIELD OF THE INVENTION[0002]This application claims priority from provisional application Serial No. 60 / 298,835 filed Jun. 15, 2001, for “Ultraviolet Light Emitting Diode.” The present invention relates to light emitting diodes (LEDs) and in particular relates to a light emitting diode formed from Group III nitrides that emit in the ultraviolet (UV) portion of the electromagnetic spectrum. This application is related to the following copending applications, each of which is incorporated entirely herein by reference: Serial No. 60 / 294,445 filed May 30, 2001, for “Multi-Quantum Well Light Emitting Diode Structure,” Serial No. 60 / 294,308 filed May 30, 2001, for “Light Emitting Diode Structure with Multi-Quantum Well and Superlattice Structure,” and Ser. No. 09 / 706,057 filed Nov. 3, 2000, for “Group III Nitride Li...

AI Technical Summary

Benefits of technology

[0011]Therefore, it is an object of the present invention to provide a light emitting diode that can produce frequencies in the ultraviolet portion of the electromagnetic spectrum and that can be incorporated into related devices and equipment, including devices that use phosphors in combination with the LED to produce white light.

Problems solved by technology

The material being used is the fundamental factor, however, because the material's full bandgap represents the limiting factor in the energy transitions that can produce a photon.

Thus, materials with smaller bandgaps cannot produce photons having sufficient energy (and corresponding wavelength and frequency) to fall into the higher energy (blue and violet) portion of the visible spectrum.

Although the blue LED has expanded the universe of LED applications, its use can be to some extent limited in producing white light for other, more mundane reasons.

Additionally, producing the necessary circuitry and physical arrangements to house and operate three LEDs is more complex than for single-color LEDs when they are incorporated into devices.

Furthermore, certain visible LED-phosphor combinations raise particular disadvantages.

Because the blue LED is stimulating the phosphorescence, however, the light always tends to have a blue component in it that may be undesired in a given application.

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