Light emitting device

• US 20030089905A1
• Filed: 11/04/2002
• Published: 05/15/2003
• Est. Priority Date: 11/09/2001
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Osame, Mitsuaki, Hayakawa, Masahiko, Anzai, Aya, Koyama, Jun, Udagawa, Makoto
• Granted Patent: US 7,723,721 B2
• Time in Patent Office: Days
• US Class Current: 257/40
• CPC Class Codes: H01L 27/12 the substrate being other than a semiconductor body, e.g. an insulating body
• CPC Class Codes: H01L 27/1222 with a particular composition, shape or crystalline structure of the active layer
• CPC Class Codes: H01L 27/124 with a particular composition, shape or layout of the wiring layers specially adapted to the circuit arrangement, e.g. scanning lines in LCD pixel circuits wiring structures per se H01L23/52
• CPC Class Codes: H01L 29/78675 with normal-type structure, e.g. with top gate
• CPC Class Codes: H01L 29/78696 characterised by the structure of the channel, e.g. multichannel, transverse or longitudinal shape, length or width, doping structure, or the overlap or alignment between the channel and the gate, the source or the drain, or the contacting structure of the channel H01L29/78612 takes precedence; transistors having a drain offset region or a lightly doped drain [LDD] H01L29/78621
• CPC Class Codes: H10K 50/80 Constructional details
• CPC Class Codes: H10K 59/1213 the pixel elements being TFTs
• CPC Class Codes: H10K 59/131 Interconnections, e.g. wiring lines or terminals

Abstract

The present invention provides a TFT that has a channel length particularly longer than that of an existing one, specifically, several tens to several hundreds times longer than that of the existing one, and thereby allowing turning to an on-state at a gate voltage particularly higher than the existing one and driving, and allowing having a low channel conductance gd. According to the present invention, not only the simple dispersion of on-current but also the normalized dispersion thereof can be reduced, and other than the reduction of the dispersion between the individual TFTs, the dispersion of the OLEDs themselves and the dispersion due to the deterioration of the OLED can be reduced.

Claims

1. A light emitting device having a light emitting element, the light emitting element comprising:

a cathode;

an organic compound layer in contact with the cathode; and

an anode in contact with the organic compound layer;

wherein a channel length L of a TFT connected to the light emitting element is 100 μ

m or more.

2. A light emitting device as set forth in claim 1, wherein a ratio of a channel width W of the TFT to the channel length L thereof is from 0.1 to 0.01.

3. A light emitting device according to claim 1, wherein the TFT connected to the light emitting element is a p-channel type TFT or an n-channel type TFT.

4. A light emitting device according to claim 1, wherein the TFT connected to the light emitting element, in the range that the sum of source-drain voltage Vd and threshold voltage Vth is larger than gate voltage Vg, has a channel conductance gd from 0 to 1×

10<sup>−

8</sup> S.

5. A light emitting device according to claim 1, wherein the TFT connected to the light emitting element, in the range that the sum of source-drain voltage Vd and threshold voltage Vth is larger than gate voltage Vg, has a channel conductance gd from 0 to 5×

10<sup>−

9</sup> S.

6. A light emitting device according to claim 1, wherein the light emitting device is incorporated into an electronic equipment selected from the group consisting of a personal computer, a video camera, a mobile computer, a goggle type display, a recording medium, a digital camera, a mobile phone and a display.

8. A light emitting device according to claim 6, wherein the TFT connected to the light emitting element is a p-channel type TFT or an n-channel type TFT.

9. A light emitting device according to claim 6, wherein the TFT connected to the light emitting element, in the range that the sum of source-drain voltage Vd and threshold voltage Vth is larger than gate voltage Vg, has a channel conductance gd from 0 to 1×

10<sup>−

8</sup> S.

10. A light emitting device according to claim 6, wherein the TFT connected to the light emitting element, in the range that the sum of source-drain voltage Vd and threshold voltage Vth is larger than gate voltage Vg, has a channel conductance gd from 0 to 5×

10<sup>−

9</sup> S.

11. A light emitting device according to claim 6, wherein the light emitting device is incorporated into an electronic equipment selected from the group consisting of a personal computer, a video camera, a mobile computer, a goggle type display, a recording medium, a digital camera, a mobile phone and a display.

7. A light emitting device having a light emitting element, the light emitting element comprising:

a cathode;

an organic compound layer in contact with the cathode; and

an anode in contact with the organic compound layer;

wherein a ratio of a channel width W of the TFT connected to the light emitting element to the channel length L thereof is from 0.1 to 0.01.

12. A light emitting device having a light emitting element, the light emitting element comprising:

a cathode;

an organic compound layer in contact with the cathode; and

an anode in contact with the organic compound layer;

wherein a TFT connected to the light emitting element, in the range that the sum of source-drain voltage Vd and threshold voltage Vth is larger than gate voltage Vg, has a channel conductance gd from 0 to 2×

10<sup>−

9</sup> S.

13. A light emitting device according to claim 12, wherein the TFT connected to the light emitting element is a p-channel type TFT or an n-channel type TFT.

14. A light emitting device according to claim 12, wherein the TFT connected to the light emitting element, in the range that the sum of source-drain voltage Vd and threshold voltage Vth is larger-than gate voltage Vg, has a channel conductance gd from 0 to 1×

10<sup>−

8</sup> S.

15. A light emitting device according to claim 12, wherein the TFT connected to the light emitting element, in the range that the sum of source-drain voltage Vd and threshold voltage Vth is larger than gate voltage Vg, has a channel conductance gd from 0 to 5×

10<sup>−

9</sup> S.

16. A light emitting device according to claim 12, wherein the light emitting device is incorporated into an electronic equipment selected from the group consisting of a personal computer, a video camera, a mobile computer, a goggle type display, a recording medium, a digital camera, a mobile phone and a display.

17. A light emitting device comprising:

a light emitting element having a cathode, an organic compound layer in contact with the cathode and an anode in contact with the organic compound layer;

a TFT connected to the light emitting element,

wherein the TFT comprises;

a semiconductor layer having a rectangular-shaped channel region and at least one pair of impurity regions;

a gate insulating film formed over the rectangular-shaped channel region; and

a gate electrode formed over the gate insulating film.

18. A light emitting device according to claim 17, wherein the TFT connected to the light emitting element is a p-channel type TFT or an n-channel type TFT.

19. A light emitting device according to claim 17, wherein the TFT connected to the light emitting element, in the range that the sum of source-drain voltage Vd and threshold voltage Vth is larger than gate voltage Vg, has a channel conductance gd from 0 to 1×

10<sup>−

8</sup> S.

20. A light emitting device according to claim 17, wherein the TFT connected to the light emitting element, in the range that the sum of source-drain voltage Vd and threshold voltage Vth is larger than gate voltage Vg, has a channel conductance gd from 0 to 5×

10<sup>−

9</sup> S.

21. A light emitting device according to claim 17, wherein the light emitting device is incorporated into an electronic equipment selected from the group consisting of a personal computer, a video camera, a mobile computer, a goggle type display, a recording medium, a digital camera, a mobile phone and a display.