Zinc oxide light emitting diode

• US 4,081,764 A
• Filed: 09/10/1973
• Issued: 03/28/1978
• Est. Priority Date: 10/12/1972
• Status: Expired due to Term

• Current Assignee: 3M Company
• Original Assignee: 3M Company
• Inventors: Tait, William C., Weiher, Richard L., Christmann, Marvin H.
• Primary Examiner(s): Larkins, William D.
• Application Number:
  US05/396,003
• Time in Patent Office: 1,660 Days
• Field of Search: 331/94.5 H, 313/499, 357/10, 357/15, 357/17, 357/18
• US Class Current: 372/43.01
• CPC Class Codes: H01L 21/00 Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/01006 Carbon [C]
• CPC Class Codes: H01L 2924/01047 Silver [Ag]
• CPC Class Codes: H01L 33/00 Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof H10K50/00 takes precedence; devices consisting of a plurality of semiconductor components formed in or on a common substrate and including semiconductor components having potential barriers, specially adapted for light emission H01L27/15; semiconductor lasers H01S5/00
• CPC Class Codes: H01S 5/32 comprising PN junctions, e.g. hetero- or double- heterostructures H01S5/34, H01S5/36 take precedence

Abstract

A light emitting diode comprising a single crystal of high efficiency violet fluorescing zinc oxide together with an ohmic cathode and a rectifying anode secured thereto. The diode emits near band-gap radiation at room temperature when energized with low D.C. voltage. The produced light is believed to be associated with radiative recombination of free excitons.

Claims

1. A light emitting diode comprising a crystal of high efficiency violet fluorescing zinc oxide, a substantially ohmic cathode secured to a portion of the crystal and a rectifying anode secured to another portion of the crystal, which diode emits light at room temperature when a low electrical potential is applied across said cathode and anode, wherein the zinc oxide crystal is a thin z-cut slab sectioned from a single crystalline boule and wherein the rectifying anode is secured to an oxygen face of said slab.

2. A diode according to claim 1, wherein the zinc oxide crystal is characterized by fluorescent efficiency at 77°

K of not less than 0.001 and a carrier concentration of not less than 10¹⁷ electrons per cm³.

3. A diode according to claim 1, wherein the substantially ohmic cathode comprises a material having a work function not appreciably greater than the work function of zinc oxide.

4. A diode according to claim 3, wherein said cathode material consists of indium or zinc.

5. A diode according to claim 3, wherein said cathode material consists of transparent conductive oxides of tin, indium or mixtures thereof.

6. A diode according to claim 1, wherein said rectifying anode comprises gold, platinum, carbon, silver or copper.

7. A diode according to claim 1, wherein the rectifying anode contains at least one point contact.

8. A diode according to claim 7, wherein the point contacts comprise a conductive paint secured to a crystal surface substantially free of destruction layers, which paint comprises gold particles dispersed in a silicate binder.

9. A diode according to claim 1, further comprising a layer of luminescent material secured to receive light emitted from the zinc oxide crystal and to emit light of a second wavelength in response to said received zinc oxide emitted light.

10. A diode according to claim 1, wherein the zinc oxide crystal has opposing major faces and the cathode and anode comprise layers evaporated onto said faces.

11. A diode according to claim 10, further comprising electrical contacts and means for holding the electrical contacts under pressure against the evaporated layers to facilitate passage of electrical current.

12. A diode according to claim 1, wherein each cathode and anode is a conductive paint, foil or evaporated film.

13. A diode according to claim 1, in which said crystal consists of a pure crystal of high efficiency violet fluorescing zinc oxide.

14. A diode according to claim 1, in which said crystal consists of an untreated crystal of high efficiency violet fluorescing zinc oxide.

15. A diode according to claim 1, wherein said crystal is further fabricated to have a pair of optically parallel and at least partially reflective faces to form a resonant cavity for the production of coherent emission.

16. A light emitting diode according to claim 1, wherein the rectifying anode comprises an array of isolated anodes on a surface of the zinc oxide crystal and the substantially ohmic cathode is secured to a portion of the crystal selected so as not to impede the emission of light from the vicinity of each of said array of isolated anodes.

17. A diode according to claim 7, wherein the point contact has an active barrier area having an average diameter of not more than 0.5 micrometers.

18. A diode according to claim 7, wherein a number of point contacts are contained within the rectifying anode.