HIGH EFFICIENCY LEDS WITH TUNNEL JUNCTIONS

• US 20100224860A1
• Filed: 05/18/2010
• Published: 09/09/2010
• Est. Priority Date: 02/23/2006
• Status: Active Grant

• Current Assignee: Creeled Incorporated
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: IBBETSON, James P., Keller, Bernd P., Mishra, Umesh K.
• Granted Patent: US 8,324,637 B2
• Time in Patent Office: Days
• US Class Current: 257/13
• CPC Class Codes: H01L 33/0016 having at least two p-n junctions
• CPC Class Codes: H01L 33/04 with a quantum effect structure or superlattice, e.g. tunnel junction
• CPC Class Codes: H01L 33/08 with a plurality of light emitting regions, e.g. laterally discontinuous light emitting layer or photoluminescent region integrated within the semiconductor body H01L27/15 takes precedence
• CPC Class Codes: H01L 33/32 containing nitrogen

Abstract

An LED made from a wide band gap semiconductor material and having a low resistance p-type confinement layer with a tunnel junction in a wide band gap semiconductor device is disclosed. A dissimilar material is placed at the tunnel junction where the material generates a natural dipole. This natural dipole is used to form a junction having a tunnel width that is smaller than such a width would be without the dissimilar material. A low resistance p-type confinement layer having a tunnel junction in a wide band gap semiconductor device may be fabricated by generating a polarization charge in the junction of the confinement layer, and forming a tunnel width in the junction that is smaller than the width would be without the polarization charge. Tunneling through the tunnel junction in the confinement layer may be enhanced by the addition of impurities within the junction. These impurities may form band gap states in the junction.

Claims

1. A high efficiency wide band gap semiconductor photonic device p-type confinement layer comprising:

a first semiconductor layer having a first composition in metallic contact with and disposed between second and third semiconductor layers having compositions dissimilar to said first layer, said second semiconductor layer being p-type, and said third semiconductor layer being n-type; and

a tunnel junction, having a tunnel width and a resistance to tunneling, formed from said second, first and third layers, adapted to permit charge carriers in said second layer to transition into charge carriers having an opposite polarity, wherein a natural dipole associated with said dissimilar materials is used to form said junction such that said width is smaller than a width in said junction would be in the absence of said first layer.

2. The apparatus of claim 1, wherein said semiconductor comprises a periodic table group III-nitride material systems.

3. The apparatus of claim 1, wherein said first layer is approximately 0.3 to 5 nanometers thick.

4. The apparatus of claim 1, wherein said first layer comprises a InxGayN layer sandwiched between said highly doped n-type GaN layer and said highly doped p-type GaN layer, where x+y=1.

5. The apparatus of claim 1, wherein said first layer comprises AlxGayN sandwiched between said highly doped p-type GaN layer and said highly doped n-type GaN layer, where x+y=1.

6. The apparatus of claim 1, wherein said junction comprises an impurity located in said second and third layers near said junction forming band gap states within said width.

7. The apparatus of claim 6, further comprising a plurality of energetically distinct impurities located in said second and third layers near said junction forming a plurality of band gap states that provide a quasi-continuous tunneling path within said width.

8. The apparatus of claim 6, wherein said impurities are the result of a placement in the junction region comprising one of the group consisting of native defects in semiconductor material, dislocations, extended crystal defects, metallic or semi-metallic islands or quantum wells, doping with rare earth impurities, doping with metal ions, implantation and impurity diffusion.

9. The apparatus of claim 7, further comprising a n-type side of said junction, and a p-type side of said junction, wherein said states form a like type of carrier on their respective sides of said junction.

10. The apparatus of claim 9, wherein said junction comprises an n-type junction layer having a charge carrier concentration of about 6×

1019/cm3 or higher.

11. The apparatus of claim 9, wherein said junction comprises a p-type junction layer having a charge carrier concentration of about 3×

1019/cm3 or higher.

12. The apparatus of claim 1, wherein said junction provides an efficient method of lateral current spreading.

13. The apparatus of claim 1, wherein said junction allows replacement of a light absorbing p-ohmic contact metal with a highly reflective n-ohmic contact metal.

14. The apparatus of claim 1, wherein a plurality of said junctions allows a plurality of vertically integrated bipolar active regions to be in series.

15. The apparatus of claim 1, wherein said junction allows inverting the polarity of a light emitting diode structure.

16. A method of fabricating a low resistance p-type confinement layer having a tunnel junction in a wide band gap semiconductor device comprising:

generating a polarization charge in said confinement layer junction, and

forming a tunnel width such that said width is smaller than the width that would form in the absence of said charge.

17. The method of claim 16, further comprising introducing an impurity at or near said junction that generates a band gap state within said width, and forming a tunnel width having a resistance to tunneling that is smaller than the resistance that would form in the absence of said impurity.

18. The method of claim 16, further comprising introducing a plurality of impurities at or near said junction that generate a plurality of energetically distinct band gap states within said width, and forming a tunnel width that is similar to a metal like transition having a quasi-continuous tunneling path within said width.

19. The method of claim 16, wherein said junction provides an efficient method of lateral current spreading.

20. The method of claim 16, wherein said junction allows replacement of a light absorbing p-ohmic contact metal with a highly reflective n-ohmic contact metal.

21. The method of claim 16, wherein a plurality of said junctions allows a plurality of vertically integrated bipolar active regions to be in series.

22. The method of claim 16, wherein said junction allows inverting the polarity of a light emitting diode structure.

23. A high efficiency wide band gap material device comprising:

a first n-type contact layer having a first composition, a first side and a second side;

a first p-type contact layer having a second composition, a first side, a second side, said second side of said first n-type contact layer in metallic contact with said first side of said first p-type contact layer;

a second p-type contact layer having said first composition, a first side, a second side, said second side of said first p-type contact layer in metallic contact with said first side of said second p-type contact layer forming a tunnel junction among said first n-type contact layer and said first and second p-type contact layers;

an active region having a first side and a second side, said first side in metallic contact with said second side of said second p-type contact layer; and

a second n-type contact layer having a first side and a second side, said first side of said second n-type contact layer in metallic contact with said second side of said active region, said tunnel junction having a tunnel width and a resistance to tunneling, wherein a natural dipole associated with dissimilar materials is used across said junction such that said width is smaller than a width in said junction would be in the absence of said first p-type layer.

24. The apparatus of claim 23, further comprising a plurality of impurities located in said first n and p type contact layers near said junction forming band gap states within said width.

25. The apparatus of claim 23, further comprising a plurality of energetically distinct impurities located in said first n- and p-type contact layers near said junction forming a plurality of energetically distinct band gap states within said width that provide a quasi-continuous tunneling path across said junction.

26. A light emitting diode (LED), comprising:

a plurality emitter structures arranged on top of each other in vertical alignment, each of said emitter structures comprising;

a first n-type layer;

a p-type layer; and

an active region sandwiched between said n-type and p-type layers;

a plurality of second n-type layers, one of which is arranged between adjacent emitter structures and one of which is arranged above the top emitter structure; and

a plurality of tunnel junctions each of which is between one of said plurality of second n-type layers and the p-type layer of the one of said plurality of emitter structures below said one of said plurality of n-type layers, bias applied across said first n-type layer in the bottom most of said emitter structures and the top one of said second n-type layers causing said active regions in said plurality of emitter structures to emit light.