Light emitting device having stacked multiple LEDS

1. A light emitting device, comprising:

a heterostructure having a plurality of light emitting diodes (LEDs) stacked one on top of another, each of the LEDs comprising a p-type semiconductor layer, an n-type semiconductor layer, and an active layer between and in contact with the p-type semiconductor layer and the n-type semiconductor layer,

wherein the LEDs are stacked without an intervening substrate layer.

2. The light emitting device of claim 1 , wherein each of the LEDs is configured to be independently biased.

3. The light emitting device of claim 1 , wherein each of the LEDs has independently controllable light output.

4. The light emitting device of claim 1 , further comprising an ohmic contact layer provided between two of the LEDs.

5. The light emitting device of claim 1 , further comprising a substrate, wherein the LEDs are provided on one side of the substrate.

6. The light emitting device of claim 5 , wherein the substrate is conductive and transparent.

7. The light emitting device of claim 6 , wherein at least one of the LEDs is configured to be biased through the substrate.

8. The light emitting device of claim 6 , further comprising a reflective surface provided on a side of the substrate that is opposite the side on which the LEDs are provided.

9. The light emitting device of claim 1 , wherein the light emitting device emits light when a voltage applied to the n-type semiconductor layer of at least one of the LEDs is equal to a voltage applied to the n-type semiconductor layer of at least another one of the LEDs.

10. The light emitting device of claim 9 , wherein the light emitting device emits light when a voltage applied to the p-type semiconductor layer of at least one of the LEDs is equal to a voltage applied to the p-type semiconductor layer of at least another one of the LEDs.

11. The light emitting device of claim 1 , wherein the light emitting device emits light when a direction of flow of an electric current across a p-n junction of at least one of the LEDs is opposite to a direction of flow of an electric current across a p-n junction of at least another one of the LEDs.

12. The light emitting device of claim 1 , wherein each of the LEDs emits a light of a different wavelength.

13. The stacked LED of claim 1 , further comprising a common electrode coupled between the first LED and the second LED.

14. A method for producing a light emitting device, comprising:

forming a plurality of light emitting diodes (LEDs), each of the LEDs comprising a p-type semiconductor layer, an n-type semiconductor layer, an active layer between and in contact with the p-type semiconductor layer and the n-type semiconductor layer, and a substrate layer in contact with one of the p-type semiconductor layer or the n-type semiconductor layer;

removing at least one substrate layer of at least one of the LEDs; and

stacking the LEDs one on top of another without an intervening substrate layer between each of the LEDs, the LEDs being stacked so as to form a layered structure.

15. The method of claim 14 , further comprising configuring each of the LEDs to be independently biased.

16. The method of claim 14 , further comprising configuring each of the LEDs to have independently controllable luminance.

17. The method of claim 14 , further comprising providing an ohmic contact layer between two of the LEDs.

18. The method of claim 14 , further comprising providing the LEDs on one side of a substrate.

19. The method of claim 18 , wherein the substrate is conductive and transparent.

20. The method of claim 19 , further comprising configuring at least one of the LEDs to be biased through the substrate.

21. The method of claim 19 , further comprising providing a reflective surface on a side of the substrate that is opposite the side on which the LEDs are provided.

22. A method for producing light from a light emitting device having a plurality of light emitting diodes (LEDs), wherein the plurality of LEDs are stacked one on top of another so as to form a layered structure, and wherein each of the LEDs includes a n- type semiconductor layer and a p-type semiconductor layer, the method comprising:

applying a first voltage to one of the p-type semiconductor layer or the n-type semiconductor layer of a first LED of the LEDs through a common electrode coupled between the first LED and a second LED of the LEDs; and

applying the first voltage to one of the p-type semiconductor layer or the n-type semiconductor layer of the second LED through the common electrode.

23. The method of claim 22 , further comprising:

applying a second voltage to one of the n-type semiconductor layer or the p-type semiconductor layer of the second LED of the LEDs through a second common electrode coupled between the second LED and a third LED of the LEDs; and

applying the second voltage to one of the n-type semiconductor layer or the p-type semiconductor layer of the third LED through the second common electrode.

24. The method of claim 23 , wherein the light emitting device has a NPPNNP layered structure and the second voltage is applied through the second common electrode to the p-type semiconductor layer of the second LED and the p-type semiconductor layer of the third LED.

25. The method of claim 22 , further comprising:

inducing a first electric current across a p-n junction of the first LED; and

inducing a second electric current across a p-n junction of the second LED,

wherein a direction of flow of the first electric current is opposite to a direction of flow of the second electric current.

26. The method of claim 22 , further comprising causing each of the LEDs to emit a light of a different wavelength.

27. The method of claim 22 , wherein the light emitting device has a PNNP layered structure and the first voltage is applied through the common electrode to the n-type semiconductor layer of the first LED and the n-type semiconductor layer of the second LED.

28. A stacked light emitting device (LED), comprising:

a first LED comprising a p-type layer, an n-type layer, and an active layer between and contacting with the p-type layer and the n-type layer;

a second LED comprising a p-type layer, an n-type layer, and an active layer between and contacting with the p-type layer and the n-type layer; and

an ohmic contact layer between and contacting with one of the p-type layer or the n-type layer of the first LED and one of the p-type layer or the n-type layer of the second LED.

29. A method for producing a light emitting device (LED), comprising:

forming a first LED with a first LED p-type layer, a first LED n-type layer, an active layer between and contacting with the first LED p-type layer and the first LED n-type layer, and a first LED substrate layer contacting the first LED n-type layer;

forming a second LED with a second LED p-type layer, a second LED n-type layer, an active layer between and contacting with the second LED p-type layer and the second LED n-type layer, and a second LED substrate layer contacting the second LED n-type layer;

forming an ohmic contact layer on the first LED p-type layer;

removing the second LED substrate layer; and

stacking the second LED onto the first LED with the second LED n-type layer contacting the ohmic contact layer.

30. The method of claim 29 , comprising:

forming a temporary substrate layer on the second LED p-type layer before removing the second LED substrate layer;

removing the first LED substrate layer;

forming a new substrate layer on the first LED n-type layer; and

removing the temporary substrate layer.