USRE45059EExpiredUtility

Group III nitride LED with undoped cladding layer

61
Assignee: EDMOND JOHN ADAMPriority: Jan 16, 2001Filed: Apr 4, 2012Granted: Aug 5, 2014
Est. expiryJan 16, 2021(expired)· nominal 20-yr term from priority
Inventors:John EdmondKathleen Marie DoverspikeHua-Shuang KongMichael John Bergmann
H10H 20/812H10H 20/825H01S 5/34333H01S 5/343H01S 5/32341B82Y 20/00
61
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Claims

Abstract

The present invention is a semiconductor structure for light emitting devices that can emit in the red to ultraviolet portion of the electromagnetic spectrum. The semiconductor structure includes a Group III nitride active layer positioned between a first n-type Group III nitride cladding layer and a second n-type Group III nitride cladding layer, the respective bandgaps of the first and second n-type cladding layers being greater than the bandgap of the active layer. The semiconductor structure further includes a p-type Group III nitride layer, which is positioned in the semiconductor structure such that the second n-type cladding layer is between the p-type layer and the active layer.

Claims

exact text as granted — not AI-modified
That which is claimed is: 
     
       1. A semiconductor structure for light emitting devices that can emit in the red to ultraviolet portion of the electromagnetic spectrum, said structure comprising:
 a first n-type layer of Al x In y Ga 1-x-y N, where 0≦x≦1 and 0≦y<1 and 0<(x+y)≦1 (x+y)≦1; 
 a second n-type layer of Al x In y Ga 1-x-y N, where 0≦x≦1 and 0≦y<1 and 0(x+y)≦1 (x+y)≦1, wherein said second n-type layer is undoped; 
 an active layer of Al x In y Ga 1-x-y N, where 0≦x<1 and 0≦y≦1 and (x+y)≦1, wherein said active layer is n-type and is positioned between said first n-type layer and said second n-type layer; and 
 a p-type layer of a Group III nitride on said second n-type layer, wherein said second n-type layer forms a p-n junction with is positioned between said p-type layer and said active layer; and 
 a third n-type layer of Al x In y Ga 1-x-y N, where 0≦x≦1 and 0≦y<1 and (x+y)≦1, wherein said third n-type layer is positioned between said second n-type layer and said p-type layer,  
 wherein said n-type layers have a higher fraction of gallium than said active layer, such that said first and second n-type layers have respective bandgaps that are each larger than the bandgap of said active layer, and wherein at least one of said first and second n-type layers comprises aluminum. 
 
     
     
       2. A semiconductor structure according to  claim 1 , wherein said active layer has a first surface and a second surface, said first surface of said active layer being in contact with said first n-type layer and said second surface of said active layer being in contact with said second n-type layer. 
     
     
       3. A semiconductor structure according to  claim 1 , wherein said second n-type layer has a first surface and a second surface, said first surface of said second n-type layer being in contact with said active layer, and said second surface of said second n-type layer being in contact with said p-type layer, wherein the a composition of said second n-type layer at least one of the layers between said active layer and said p-type layer is progressively graded such that the crystal lattice at said first surface of said second n-type layer more closely matches the crystal lattice of said active layer, and the crystal lattice at said second surface of said second n-type layer more closely matches the crystal lattice of said p-type layer. 
     
     
       4. A semiconductor structure according to  claim 1 , wherein said p-type layer is in contact with said second third n-type layer, opposite said active layer. 
     
     
       5. A semiconductor structure according to  claim 1 , wherein said second n-type layer consists essentially of Al x Ga 1-x N, where 0<x<1. 
     
     
       6. A semiconductor structure according to  claim 1 , wherein said active layer consists essentially of In y Ga 1-y N, where 0<y<1. 
     
     
       7. A semiconductor structure according to  claim 1 , wherein said p-type layer is magnesium-doped gallium nitride. 
     
     
       8. A semiconductor structure according to  claim 7 , wherein said second n-type layer is thick enough to deter migration of magnesium from said p-type layer to said active layer, yet thin enough to facilitate recombination in said active layer. 
     
     
       9. A semiconductor structure according to  claim 1 , wherein said p-type layer is indium nitride. 
     
     
       10. A semiconductor structure according to  claim 1 , wherein said p-type layer is In x Ga 1-x N, where 0<x<1. 
     
     
       11. A semiconductor structure according to  claim 1 , wherein said p-type layer comprises a superlattice formed from a plurality of Group III nitride layers selected from the group consisting of gallium nitride, indium nitride, and In x Ga 1- x N, where 0<x<1. 
     
     
       12. A semiconductor structure according to  claim 11 , wherein said superlattice is formed from alternating layers of two Group III nitride layers selected from the group consisting of gallium nitride, indium nitride, and In x Ga 1-x N, where 0<x<1. 
     
     
       13. A semiconductor structure according to  claim 1 , further comprising a wherein:
 the first n-type layer comprises Al x In y Ga 1-x-y N, where 0≦x≦1 and 0≦y<1 and 0<(x+y)≦1; 
 the second n-type layer comprises Al x In y Ga 1-x-y N, where 0≦x≦1 and 0≦y<1 and 0<(x+y)≦1; and 
 the third n-type layer of Al x In y Ga 1-x-y N, where 0≦x≦1 and 0≦y<1 and (x+y)≦1, wherein said third n-type layer is positioned between said second n-type layer and forms a p-n junction with said p-type layer. 
 
     
     
       14. A semiconductor structure according to  claim 13 , wherein said third n-type layer has a first surface and a second surface, said first surface of said third n-type layer being in contact with said p-type layer and said second surface of said third n-type layer being in contact with said second n-type layer. 
     
     
       15. A semiconductor structure according to  claim 1 , further comprising an n-type silicon carbide substrate, wherein said first n-type layer is positioned between said silicon carbide substrate and said active layer. 
     
     
       16. A semiconductor structure according to  claim 15 , further comprising discrete crystal portions selected from the group consisting of gallium nitride and indium gallium nitride, said discrete crystal portions positioned between said first n-type layer and said silicon carbide substrate, said discrete crystal portions being present in an amount sufficient to reduce the baffler between said first n-type layer and said silicon carbide substrate, but less than an amount that would detrimentally affect the function of any resulting light emitting device formed on said silicon carbide substrate. 
     
     
       17. A semiconductor structure according to  claim 1 , further comprising:
 an n-type-silicon carbide substrate; and 
 a conductive buffer layer positioned between said silicon carbide substrate and said first n-type layer. 
 
     
     
       18. A semiconductor structure according to  claim 17 , wherein said conductive buffer layer has a first surface and a second surface, said first surface of said conductive buffer layer being in contact with said silicon carbide substrate and said second surface of said conductive buffer layer being in contact with said first n-type layer. 
     
     
       19. A semiconductor structure according to  claim 17 , wherein said conductive buffer layer consists essentially of aluminum gallium nitride having the formula Al x Ga 1-x N, where 0<x<1. 
     
     
       20. A semiconductor structure according to  claim 17 , further comprising an n-type transition layer of a Group III nitride, said transition layer being positioned between said conductive buffer layer and said first n-type layer. 
     
     
       21. A semiconductor structure according to  claim 17 , further comprising discrete crystal portions selected from the group consisting of gallium nitride and indium gallium nitride, said discrete crystal portions positioned between said conductive buffer layer and said silicon carbide substrate, said discrete crystal portions being present in an amount sufficient to reduce the barrier between said conductive buffer layer and said silicon carbide substrate, but less than an amount that would detrimentally affect the function of any resulting light emitting device formed on said silicon carbide substrate. 
     
     
       22. A semiconductor structure for light emitting devices that can emit in the red to ultraviolet portion of the electromagnetic spectrum, said structure comprising:
 a first n-type layer of Al x In y Ga 1-x-y N, where 0≦x≦1 and 0≦y<1 and (x+y)≦1; 
 a second n-type layer of Al x In y Ga 1-x-y N, where 0≦x<1 and 0≦y <1 and (x+y)≦1, wherein said second n-type layer is an undoped layer having a first surface and a second surface; 
 an active layer of Al x In y Ga 1-x-y N, where 0≦x<1 and 0≦y≦1 and (x+y)≦1, wherein said active layer is n-type and is positioned between said first n-type layer and the first surface of said second n-type layer; and 
 a p-type layer of a Group III nitride, wherein said second n-type layer is positioned between said p-type layer and said active layer; 
 wherein said first and second n-type layers have respective bandgaps that are each larger than the bandgap of said active layer; and wherein at least one of said first layer and said second n-type layer is compositionally graded in steps from said first surface to said second surface. 
 
     
     
       23. A semiconductor structure according to  claim 22 , wherein said second layer is compositionally graded such that a crystal lattice at said a first surface of said second n-type layer proximate said active layer substantially matches a crystal lattice of said active layer. 
     
     
       24. A semiconductor structure according to  claim 22 , wherein said first layer is n-type layer and is compositionally graded in steps such that a crystal lattice at a first surface of said first n-type layer proximate said active layer substantially matches a crystal lattice of said active layer. 
     
     
       25. A semiconductor structure for light emitting devices that can emit in the red to ultraviolet portion of the electromagnetic spectrum, said structure comprising:
 a first n-type layer of Al x In y Ga 1-x-y N, where 0≦x≦1 and 0≦y<1 and (x+y)≦1; 
 a second n-type layer of Al x In y Ga 1-x-y N, where 0≦x≦1 and 0≦y<1 and (x+y)≦1, wherein said second n-type layer is undoped; 
 an active layer of Al x In y Ga 1-x-y N, where 0≦x<1 and 0≦y≦1 and (x+y)≦1, wherein said active layer is n-type and is positioned between said first n-type layer and said second n-type layer; and 
 a p-type superlattice formed of layers of Group III nitrides, wherein said second n-type layer is positioned between said p-type superlattice and said active layer. 
 
     
     
       26. A semiconductor structure according to  claim 25  for light emitting devices, said structure comprising:
 a first n-type layer of Al x In y Ga 1-x-y N, where 0≦x≦1 and 0≦y<1 and (x+y)≦1; 
 a second n-type layer of AlxIn y Ga 1-x-y N, where 0≦x≦1 and 0≦y<1 and (x+y)≦1, wherein said second n-type layer is undoped; 
 an active layer of Al x In y Ga 1-x-y N, where 0≦x<1 and 0≦y≦1 and (x+y)≦1, wherein said active layer is n-type and is positioned between said first n-type layer and said second n-type layer; 
 p-type layers of Group III nitrides, wherein said second n-type layer is positioned between said p-type layers and said active layer; and  
 wherein said p-type layers of said p-type superlattice are selected from the group consisting of gallium nitride, indium nitride, and In x Ga 1-x N, where 0<x<1. 
 
     
     
       27. A semiconductor structure according to  claim 25 , wherein said superlattice is formed from alternating layers of two Group III nitride layers selected from the group consisting of gallium nitride, indium nitride, and In x Ga 1-x N, where 0<x<1. 
     
     
       28. A semiconductor structure according to  claim 25 , further for light emitting devices, said structure comprising:
 a first n-type layer of Al x In y Ga 1-x-y N, where 0≦x≦1 and 0≦y<1 and (x+y)≦1; 
 a second n-type layer of AlxIn y Ga 1-x-y N, where 0≦x≦1 and 0≦y<1 and (x+y)≦1, wherein said second n-type layer is undoped; 
 an active layer of Al x In y Ga 1-x-y N, where 0≦x<1 and 0≦y≦1 and (x+y)≦1, wherein said active layer is n-type and is positioned between said first n-type layer and said second n-type layer; 
 p-type layers of Group III nitrides, wherein said second n-type layer is positioned between said p-type layers and said active layer; and  
 a third n-type layer of Al x In y Ga 1-x-y N, where 0≦x≦1 and 0≦y<1 and (x+y)≦1, wherein said third n-type layer is positioned between said second n-type layer and said p-type superlattice layers. 
 
     
     
       29. A semiconductor structure according to  claim 28 , wherein said third n-type layer has a first surface and a second surface, said first surface of said third n-type layer being in contact with one of said p-type superlattice layers and said second surface of said third n-type layer being in contact with said second n-type layer. 
     
     
       30. The structure of claim 23, wherein the p-type layer comprises In x Ga 1-x N wherein 0≦x≦1.  
     
     
       31. The structure of claim 30, wherein the second layer is an n-type layer that is doped or undoped.  
     
     
       32. A semiconductor structure for a light emitting device, comprising:
 a first Group III nitride layer comprising n-type Al x In y Ga 1-x-y N wherein 0≦x≦1 and 0≦y<1 and (x+y)≦1;   a Group III nitride based active layer comprising a quantum well on the first Group III nitride layer;   a second Group III nitride layer on the active layer opposite the first Group III nitride layer, the second Group III nitride layer comprising n-type Al x In y Ga 1-x-y N wherein 0≦x≦1 and 0≦y<1 and (x+y)≦1; and   a third Group III nitride layer on the second Group III nitride layer opposite the active layer, the third Group III nitride layer comprising n-type Al x In y Ga 1-x-y N wherein 0≦x≦1 and 0≦y<1 and (x+y)≦1,   wherein at least one of the first and second Group III nitride layers comprises aluminum.    
     
     
       33. The structure of claim 32, wherein the at least one of the first and second Group III nitride layers has a higher fraction of aluminum than the active layer.  
     
     
       34. The structure of claim 32, wherein the second Group III nitride layer comprises Al x Ga 1-x N wherein 0<x<1.  
     
     
       35. The structure of claim 32, further comprising:
 a fourth Group III nitride layer on the third Group III nitride layer opposite the second Group III nitride layer.    
     
     
       36. The structure of claim 35, wherein the fourth Group III nitride layer comprises n-type Al x In y Ga 1-x-y N wherein 0≦x≦1 and 0≦y<1 and (x+y)≦1.  
     
     
       37. The structure of claim 35, wherein at least one of the second, third, and fourth Group III nitride layers is undoped.  
     
     
       38. The structure of claim 35, wherein the fourth Group III nitride layer comprises a magnesium-doped p-type Group III nitride layer comprising In x Ga 1-x N wherein 0≦x≦1.  
     
     
       39. The structure of claim 38, wherein the fourth Group III nitride layer comprises a superlattice formed from a plurality of Group III nitride layers selected from the group consisting of gallium nitride, indium nitride, and In x Ga 1-x N wherein 0<x<1.  
     
     
       40. The structure of claim 32, wherein at least one of the first and second Group III nitride layers is graded.  
     
     
       41. A semiconductor structure for a light emitting device, comprising:
 a first Group III nitride layer comprising Al x In y Ga 1-x-y N wherein 0≦x≦1 and 0≦y<1 and (x+y)≦1;   a Group III nitride based active layer comprising a quantum well on the first Group III nitride layer;   a second Group III nitride layer comprising Al x In y Ga 1-x-y N wherein 0≦x≦1 and 0≦y<1 and (x+y)≦1 on the active layer opposite the first Group III nitride layer;   a third Group III nitride layer comprising n-type Al x In y Ga 1-x-y N wherein 0≦x≦1 and 0≦y<1 and (x+y)≦1 on the second Group III nitride layer opposite the active layer; and   a fourth Group III nitride layer comprising Al x In y Ga 1-x-y N wherein 0≦x≦1 and 0≦y<1 and (x+y)≦1 on the third Group III nitride layer opposite the second Group III nitride layer,   wherein at least one of the first and second Group III nitride layers comprises aluminum, and wherein at least one of the second, third, and fourth Group III nitride layers is undoped.    
     
     
       42. The structure of claim 41, wherein the fourth Group III nitride layer comprises p-type In x Ga 1-x N wherein 0≦x≦1.  
     
     
       43. The structure of claim 42, wherein one of the layers between the active layer and the fourth Group III nitride layer comprises a graded layer.  
     
     
       44. The structure of claim 41, wherein at least one of the first and second Group III nitride layers comprises a graded n-type layer.

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