Micrometer scale light emitting diode displays on patterned templates and substrates
A uLED and method for regrowth with thinner deposition on sidewall are disclosed. The uLED and method include a growth substrate including flat first and second regions, where the growth substrate is thicker in the first region as compared to the second region, and a third region of sloped sidewalls connecting the first and second regions, the topography forming a regular geometric pattern, a plurality of semiconductor epitaxial layers covering the first, second, and third regions including at least a p-n junction layer including a light emitting active region of direct bandgap semiconductor, sandwiched between n-type and p-type layers, each of the plurality of semiconductor epitaxial layers being thicker on the first and second regions as compared to the corresponding semiconductor epitaxial layers on the third region, and a plurality of electrical contacts forming an anode and cathode on part of the first and second regions, respectively.
1. A micrometer scale light emitting diode (uLED) comprising:
a growth substrate comprising flat first and second regions, where the growth substrate is thicker in the first region as compared to the second region, and a third region of sloped sidewalls connecting the first and second regions, the topography forming a regular geometric pattern;
a plurality of semiconductor epitaxial layers covering the first, second, and third regions comprising: at least a p-n junction layer including a light emitting active region of direct bandgap semiconductor, sandwiched between n-type and p-type layers, wherein of the plurality of semiconductor epitaxial layers is thicker on the first and second regions as compared to the corresponding semiconductor epitaxial layers on the third region;
an n-contact on the n-layer and a p-contact on the p-layer; and
at least one layer of light converting phosphor.
2. The uLED of claim 1 , wherein the thinner epitaxial layers on the sidewall enables a high resistance to hole current between the n-contact and the p-contact, confining greater than 90% of forward bias hole injection to the first region.
3. The uLED of claim 2 , wherein the high resistance is greater than 800 ohm/square.
4. The uLED of claim 1 , wherein a perimeter of the first region forms a regular polygon having a number of sides greater than 3 and pitch less than 150 micrometers, a nd the angle between the first region and third region is between 95 and 120 degrees.
5. The uLED of claim 1 , wherein the surfaces distal to the n-contact and the p-contact are within 1 micrometer of the same height.
6. The uLED of claim 1 further comprising a supporting underfill.
7. The uLED of claim 1 further being coupled to a thin film transistor (TFT) backplane chip.
8. The uLED of claim 1 , further including an optics to control emission angle of light.
9. The uLED of claim 1 further including a ridge of reflecting material to form a barrier to contain the phosphor and reflect light back into the phosphor to thereby provide optical isolation.
10. A micrometer scale light emitting diode (uLED) comprising:
a growth substrate comprising: flat first and second regions, where the growth substrate is thicker in the first region as compared to the second region, and a third region of sloped sidewalls connecting the first and second regions, the topography forming a regular geometric pattern;
a plurality of semiconductor epitaxial layers covering the first, second, and third regions including at least a p-n junction layer including a light emitting active region of direct bandgap semiconductor, sandwiched between n-type and p-type layers, each of the plurality of semiconductor epitaxial layers being thicker on the first and second regions as compared to the corresponding semiconductor epitaxial layers on the third region;
an n-contact on the n-layer and a p-contact on the p-layer; and
supporting underfill.
11. The uLED of claim 10 , wherein the thinner epitaxial layers on the sidewall enables a high resistance to hole current between the n-contact and the p-contact, confining greater than 90% of forward bias hole injection to the first region.
12. The uLED of claim 11 , wherein the high resistance is greater than 800 ohm/square.
13. The uLED of claim 10 , wherein a perimeter of the first region forms a regular polygon having a number of sides greater than 3 and pitch less than 150 micrometers, and the angle between the first region and third region is between 95 and 120 degrees.
14. The uLED of claim 10 , wherein the surfaces distal to the n-contact and p-contact are within 1 micrometer of the same height.
15. The uLED of claim 11 , wherein the uLED is coupled to a thin film transistor (TFT) backplane chip.
16. The uLED of claim 11 , further including an optic to control emission angle of light.
17. The uLED of claim 11 , further including a ridge of reflecting material to form a barrier to contain the phosphor and reflect light back into the phosphor to thereby provide optical isolation.
18. A micrometer scale light emitting diode (uLED) wherein the uLED has a characteristic dimension of less than 100 micrometers, the uLED comprising:
a growth substrate comprising: a flat first region, a flat second region, and a third region of sloped sidewalls connecting the first and second regions, the topography forming a regular geometric pattern;
a plurality of semiconductor epitaxial layers covering the first, second, and third regions including at least a p-n junction layer including a light emitting active region of direct bandgap semiconductor, sandwiched between n-type and p-type layers, each of the plurality of semiconductor epitaxial layers being thicker on the first and second regions as compared to the corresponding semiconductor epitaxial layers on the third region; and
an n-contact on the n-layer and a p-contact on the p-layer;
wherein the uLED is coupled to a thin film transistor (TFT) backplane chip.
19. The uLED of claim 1 having a characteristic dimension of less than 100 micrometers.
20. The uLED of claim 10 having a characteristic dimension of less than 100 micrometers.