High capacitance pixel for electronic displays

• US 6,072,278 A
• Filed: 07/20/1998
• Issued: 06/06/2000
• Est. Priority Date: 08/06/1997
• Status: Expired due to Term

• Current Assignee: Alliedsignal Inc.
• Original Assignee: Alliedsignal Inc.
• Inventors: Keyser, Thomas, Becker, Gerald D.
• Primary Examiner(s): VU, DAVID HUNG
• Application Number:
  US09/119,512
• Time in Patent Office: 687 Days
• Field of Search: 315/169.3, 315/169.1, 315/160, 313/505, 313/506, 313/509
• US Class Current: 315/169.1
• CPC Class Codes: H01L 27/15 including semiconductor components having potential barriers, specially adapted for light emission
• CPC Class Codes: H05B 33/12 Light sources with substantially two-dimensional radiating surfaces
• CPC Class Codes: H05B 33/22 characterised by the chemical or physical composition or the arrangement of auxiliary dielectric or reflective layers

Abstract

An electroluminescent device in accordance with the present invention includes a first conductive layer having a portion thereof for connecting to a gate of a blocking transistor formed on a substrate. A dielectric layer is formed on the first conductive layer, the dielectric layer having a dielectric constant of at least six. A second conductive layer is formed on the dielectric layer such that the first and second conductive layers have portions which form electrodes of a hold capacitor and the dielectric layer provides a capacitor dielectric between the electrodes such that the dielectric layer continuously covers the device. A pixel electrode is associated with and coupled to the blocking transistor. An electroluminescent stack and a transparent electrode are included wherein the electroluminescent stack is disposed between the transparent electrode and the pixel electrode such that when the blocking transistor is activated the pixel electrode associated therewith illuminates and is maintained in an illuminated state by the hold capacitor.

Claims

1. An electroluminescent device comprising:

a substrate;

a blocking transistor formed on the substrate;

a first conductive layer having a portion thereof for connecting to a gate of said blocking transistor formed on said substrate;

a dielectric layer formed on the first conductive layer, the dielectric layer including regions of reduced thickness and at least one sublayer having a dielectric constant of at least six, said at least one sublayer, having a range covering portion of said dielectric layer to the entire dielectric layer;

a second conductive layer formed on the dielectric layer such that the first and second conductive layers have portions which form electrodes of a hold capacitor and the regions of reduced thickness provide a capacitor dielectric between the electrodes;

a pixel electrode associated with and coupled to the blocking transistor; and

a transparent electrode wherein an electroluminescent stack is disposed between the transparent electrode and the pixel electrode such that when the blocking transistor is activated the pixel electrode associated therewith illuminates and is maintained in an illuminated state by the hold capacitor.

2. The electroluminescent device as recited in claim 1, wherein the dielectric layer is an oxidized portion of the first conductive layer.

3. The electroluminescent device as recited in claim 1, wherein the dielectric layer is between about 500 Å

and about 2000 Å

.

4. The electroluminescent device as recited in claim 1, wherein the dielectric layer includes a thickness of less than about 3000 Å

.

5. The electroluminescent device as recited in claim 1, wherein the dielectric layer includes silicon nitride.

6. The electroluminescent device as recited in claim 1, wherein the dielectric layer includes aluminum oxide.

7. The electroluminescent device as recited in claim 1, wherein the dielectric layer includes titanium oxide.

8. The electroluminescent device as recited in claim 1, wherein the dielectric layer includes tantalum oxide.

9. A head mount display comprising the electroluminescent device as recited in claim 1.

10. The electroluminescent device as recited in claim 1, wherein said dielectric layer further comprises a second sublayer formed from a dielectric material having a dielectric constant less than the dielectric constant of said at least one sublayer wherein the second sublayer includes a thinned thickness between the electrodes.

11. The electroluminescent device as recited in claim 10, wherein the thinned thickness is eliminated in a predetermined area between the electrodes.

12. An electroluminescent device comprising:

a first conductive layer having a portion thereof for connecting to a gate of a blocking transistor formed on a substrate;

a composite dielectric layer formed on the first conductive layer, the dielectric layer including at least two sublayers wherein one sublayer includes a high dielectric constant of at least six;

a second conductive layer formed on the composite dielectric layer such that the first and second conductive layers have portions which form electrodes of a hold capacitor and the composite dielectric layer provides a capacitor dielectric between the electrodes such that the high dielectric constant sublayer continuously covers the device;

a pixel electrode associated with and coupled to the blocking transistor; and

a transparent electrode wherein an electroluminescent stack is disposed between the transparent electrode and the pixel electrode such that when the blocking transistor is activated the pixel electrode associated therewith illuminates and is maintained in an illuminated state by the hold capacitor; and

wherein a lower dielectric constant sublayer of the composite dielectric layer includes a lower dielectric material than the high dielectric constant sublayer, said lower dielectric sublayer being disposed about and above lateral sides of the pixel electrode.

13. An electroluminescent device comprising:

a substrate;

a blocking transistor formed on said substrate;

a first conductive layer having a portion thereof for connecting to a gate of said blocking transistor;

a composite dielectric layer formed on the first conductive layer, the dielectric layer including regions of reduced thickness;

a second conductive layer formed on the composite dielectric layer such that the first and second conductive layers have portions which form electrodes of a hold capacitor and the regions of reduced thickness provide a capacitor dielectric between the electrodes such that the dielectric layer provides greater capacitance per unit area for the hold electrode;

a pixel electrode associated with and coupled to the blocking transistor; and

a transparent electrode wherein an electroluminescent stack is disposed between the transparent electrode and the pixel electrode such that when the blocking transistor is activated the pixel electrode associated therewith illuminates and is maintained in an illuminated state by the hold electrode.

14. The electroluminescent device as recited in claim 13, wherein the regions of reduced thickness are between about 500 Å

and about 2000 Å

in thickness.