Light emitting device

• US 8,008,670 B2
• Filed: 02/13/2007
• Issued: 08/30/2011
• Est. Priority Date: 02/21/2006
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Honda, Tatsuya
• Primary Examiner(s): Le; Thao P.
• Application Number:
  US11/674,410
• Publication Number:
  US 20070194334A1
• Time in Patent Office: 1,659 Days
• Field of Search: 257/13, 257/21, 257/79, 257/80, 257/82, 257/E25.032, 257/91, 257/E33.001, 257/E27.12
• US Class Current: 257/91
• CPC Class Codes: H05B 33/145 Arrangements of the electroluminescent material
• CPC Class Codes: H05B 33/20 characterised by the chemical or physical composition or the arrangement of the material in which the electroluminescent material is embedded
• CPC Class Codes: H05B 33/22 characterised by the chemical or physical composition or the arrangement of auxiliary dielectric or reflective layers

Abstract

An object is to provide a light emitting element using an inorganic compound as a light emitting material, which has ever-higher luminous efficiency and can be driven with low voltage. The chance of excitation of light emitting centers (atoms) in a light emitting layer is increased to enhance luminous efficiency by providing a carrier supply layer in order to increase the number of carries in the light emitting layer of a light emitting element using an inorganic compound, and drive voltage of the light emitting element or a light emitting device is reduced.

Claims

1. A light emitting device comprising:

a semiconductor layer of a transistor formed over a substrate;

a first electrode electrically connected to the semiconductor layer of the transistor;

a first insulating film formed over the first electrode;

a light emitting layer formed over the first insulating film;

a second insulating film formed over the light emitting layer;

a second electrode formed over the second insulating film; and

a first carrier supply layer and a second carrier supply layer interposed between the first and second insulating films,

wherein the light emitting layer is directly in contact with upper and side surfaces of the first and second carrier supply layers,

wherein the light emitting layer includes a base material and an additive material,

wherein the first and second carrier supply layers comprise a semiconductor material including at least one of an n-type impurity element and a p-type impurity element, and

wherein the semiconductor layer of the transistor includes a metal oxide.

2. The light emitting device according to claim 1, wherein the base material is one or more materials selected from the group consisting of a compound including a Group 2 element and a Group 16 element, a compound including a Group 12 element and a Group 16 element, a compound including a Group 13 element and a Group 15 element, a compound including a Group 2 element, a Group 13 element, and a Group 16 element, a compound including a plurality of Group 14 elements, and rare-earth sulfide.

3. The light emitting device according to claim 1, wherein the base material is one or more materials selected from the group consisting of calcium sulfide, strontium sulfide, barium sulfide, zinc sulfide, cadmium sulfide, zinc oxide, gallium nitride, strontium gallium sulfide, magnesium zinc oxide, silicon carbide, and yttrium sulfide.

4. The light emitting device according to claim 1, wherein the additive material is one or more materials selected from transition metal elements and rare-earth elements.

5. The light emitting device according to claim 1, wherein the additive material is one or more materials selected from the group consisting of cerium, praseodymium, samarium, europium, terbium, thulium, chromium, iron, cobalt, nickel, copper, silver, gold, platinum, and manganese.

6. The light emitting device according to claim 1, wherein the first and second carrier supply layers comprise a material selected from the group consisting of zinc sulfide to which indium is added, zinc oxide to which aluminum or gallium is added, gallium nitride to which silicon is added, zinc oxide to which nitrogen or phosphorus is added, and gallium nitride to which zinc is added.

7. An electronic device comprising the light emitting device according to claim 1 in a display portion.

15. The light emitting device according to claim 1, wherein the semiconductor layer of the transistor includes zinc.

16. The light emitting device according to claim 1, wherein the metal oxide is zinc oxide.

8. A light emitting device comprising:

a semiconductor layer of a transistor formed over a substrate;

a first electrode electrically connected to the semiconductor layer of the transistor;

a first insulating film formed over the first electrode;

a light emitting layer formed over the first insulating film;

a second insulating film formed over the light emitting layer;

a second electrode formed over the second insulating film; and

a plurality of carrier supply layers interposed between the first and second insulating films,

wherein the light emitting layer is interposed between the plurality of carrier supply layers,

wherein the light emitting layer is directly in contact with upper and side surfaces of the plurality of carrier supply layers,

wherein the light emitting layer includes a base material and an additive material,

wherein the plurality of carrier supply layers comprise a semiconductor material including at least one of an n-type impurity element and a p-type impurity element, and

wherein the semiconductor layer of the transistor includes a metal oxide.

9. The light emitting device according to claim 8, wherein the base material is one or more materials selected from the group consisting of a compound including a Group 2 element and a Group 16 element, a compound including a Group 12 element and a Group 16 element, a compound including a Group 13 element and a Group 15 element, a compound including a Group 2 element, a Group 13 element, and a Group 16 element, a compound including a plurality of Group 14 elements, and rare-earth sulfide.

10. The light emitting device according to claim 8, wherein the base material is one or more materials selected from the group consisting of calcium sulfide, strontium sulfide, barium sulfide, zinc sulfide, cadmium sulfide, zinc oxide, gallium nitride, strontium gallium sulfide, magnesium zinc oxide, silicon carbide, and yttrium sulfide.

11. The light emitting device according to claim 8, wherein the additive material is one or more materials selected from transition metal elements and rare-earth elements.

12. The light emitting device according to claim 8, wherein the additive material is one or more materials selected from the group consisting of cerium, praseodymium, samarium, europium, terbium, thulium, chromium, iron, cobalt, nickel, copper, silver, gold, platinum, and manganese.

13. The light emitting device according to claim 8, wherein the carrier supply layers comprise a material selected from the group consisting of zinc sulfide to which indium is added, zinc oxide to which aluminum or gallium is added, gallium nitride to which silicon is added, zinc oxide to which nitrogen or phosphorus is added, and gallium nitride to which zinc is added.

14. An electronic device comprising the light emitting device according to claim 8 in a display portion.

17. The light emitting device according to claim 8, wherein the semiconductor layer of the transistor includes zinc.

18. The light emitting device according to claim 8, wherein the metal oxide is zinc oxide.