Group III nitride heterostructure for optoelectronic device

Abstract

Heterostructures for use in optoelectronic devices are described. One or more parameters of the heterostructure can be configured to improve the reliability of the corresponding optoelectronic device. The materials used to create the active structure of the device can be considered in configuring various parameters the n-type and/or p-type sides of the heterostructure.

What is claimed is: 
     
       1. A heterostructure comprising:
 a substrate; 
 an AlN buffer layer located on the substrate; 
 an Al x Ga 1-x N/Al x′ Ga 1-x′ N first superlattice structure located on the buffer layer, wherein 0.6<x≤1, 0.1<x′<0.9, and x>x′, and wherein each layer in the first superlattice structure has a thickness less than or equal to one hundred nanometers; 
 an Al y Ga 1-y N/Al y′ Ga 1-y′ N second superlattice structure located on the first superlattice structure, wherein y′<x′, 0.6<y≤1, 0.1<y′<0.8, and y>y′, and wherein each layer in the second superlattice structure has a thickness less than one hundred nanometers; 
 an Al z Ga 1-z N n-type layer located on the second superlattice structure, wherein 0.1<z<0.75 and z<y′; and 
 an Al b Ga 1-b N/Al q Ga 1-q N active structure located on the n-type layer, wherein b-q>0.05. 
 
     
     
       2. The heterostructure of  claim 1 , wherein the active structure is configured to emit electromagnetic radiation having a peak emission wavelength between 300 nanometers and 360 nanometers, and wherein 0.1<x′<0.8, 0.1<y′<0.65, 0.1<z<0.6, and 0<q<0.35. 
     
     
       3. The heterostructure of  claim 1 , wherein the active structure is configured to emit electromagnetic radiation having a peak emission wavelength between 260 nanometers and 300 nanometers, and wherein 0.6<x′<0.9, 0.5<y′<0.8, 0.4<z<0.75, and 0.2<q<0.6. 
     
     
       4. The heterostructure of  claim 1 , wherein the active structure is configured to emit electromagnetic radiation having a peak emission wavelength between 230 nanometers and 260 nanometers, and wherein 0.6≤z<0.75 and 0.45<q<0.75. 
     
     
       5. The heterostructure of  claim 1 , wherein at least one of x or y equals one. 
     
     
       6. The heterostructure of  claim 1 , further comprising:
 an Al B Ga 1-B N electron blocking layer located on the active structure, wherein B is at least 1.05*b; and 
 a p-type GaN layer located on the electron blocking layer. 
 
     
     
       7. The heterostructure of  claim 6 , further comprising a graded p-type layer located between the electron blocking layer and the GaN layer, wherein the graded p-type layer has an aluminum molar fraction that decreases from B at a heterointerface between the electron blocking layer and the graded p-type layer to zero at a heterointerface between the graded p-type layer and the GaN layer. 
     
     
       8. The heterostructure of  claim 6 , wherein the GaN layer includes three sublayers, and wherein each sublayer has a doping concentration that differs from an immediately adjacent sublayer by at least ten percent. 
     
     
       9. The heterostructure of  claim 1 , further comprising a grading structure located between the second superlattice structure and the n-type layer, wherein the grading structure has an aluminum molar fraction that decreases from y′ at a heterointerface between the second superlattice structure and the grading structure to z at a heterointerface between the grading structure and the n-type layer. 
     
     
       10. The heterostructure of  claim 1 , further comprising a tensile/compressive superlattice located between the second superlattice structure and the n-type layer. 
     
     
       11. The heterostructure of  claim 1 , wherein the active structure is configured to emit electromagnetic radiation having a peak emission wavelength between 300 nanometers and 360 nanometers, wherein the n-type layer includes four sublayers, and wherein each sublayer differs from an immediately adjacent sublayer by at least one of: doping concentration or aluminum molar fraction. 
     
     
       12. The heterostructure of  claim 1 , wherein the active structure is configured to emit electromagnetic radiation having a peak emission wavelength between 260 nanometers and 300 nanometers, wherein the n-type layer includes five sublayers, and wherein each sublayer differs from an immediately adjacent sublayer by at least one of: doping concentration or aluminum molar fraction. 
     
     
       13. A heterostructure comprising:
 a substrate; 
 a buffer layer located on the substrate, wherein the buffer layer is formed of a group III nitride material including aluminum; 
 a grading structure located on the buffer layer, wherein the grading structure is formed of a group III nitride material having an aluminum molar fraction that decreases from an aluminum molar fraction at a bottom heterointerface to an aluminum molar fraction at a top heterointerface; 
 a n-type layer located on the grading structure, wherein the n-type layer is formed of a group III nitride material including aluminum having a molar fraction z, and wherein 0.1<z≤0.9; 
 an active structure including quantum wells and barriers located on the n-type layer, wherein the quantum wells are formed of a group III nitride material including aluminum having a molar fraction q and the barriers are formed of a group III nitride material including aluminum having a molar fraction b, and wherein b-q>0.05; 
 an electron blocking layer located on the active structure, wherein the electron blocking layer is formed of a group III nitride material including aluminum having a molar fraction B, and wherein B is at least 1.05*b; 
 a p-type GaN layer located on the electron blocking layer; and 
 a graded p-type layer located between the electron blocking layer and the GaN layer, wherein the graded p-type layer has an aluminum molar fraction that decreases from B at a heterointerface between the electron blocking layer and the graded p-type layer to zero at a heterointerface between the graded p-type layer and the GaN layer. 
 
     
     
       14. The heterostructure of  claim 13 , wherein the active structure is configured to emit electromagnetic radiation having a peak emission wavelength between 230 nanometers and 260 nanometers, and wherein 0.6≤z≤0.9 and 0.45<q<0.75. 
     
     
       15. The heterostructure of  claim 13 , further comprising:
 a first superlattice structure located between the buffer layer and the grading structure, wherein the first superlattice structure is formed of a plurality of periods, each period including two layers formed of group III nitride materials including aluminum and having molar fractions x and x′, where x>x′; and 
 a second superlattice structure located between the first superlattice structure and the graded structure, wherein the second superlattice structure is formed of a plurality of periods, each period including two layers formed of group III nitride materials including aluminum and having molar fractions y and y′, where y>y′. 
 
     
     
       16. The heterostructure of  claim 13 , wherein the active structure is configured to emit electromagnetic radiation having a peak emission wavelength between 300 nanometers and 360 nanometers, and wherein 0.1<x′<0.8, 0.1<y′<0.65, 0.1<z<0.6, and 0<q<0.35. 
     
     
       17. The heterostructure of  claim 13 , wherein the active structure is configured to emit electromagnetic radiation having a peak emission wavelength between 260 nanometers and 300 nanometers, and wherein 0.6<x′<0.9, 0.5<y′<0.8, 0.4<z<0.75, and 0.2<q<0.6. 
     
     
       18. The heterostructure of  claim 15 , wherein z<y′<x′. 
     
     
       19. An optoelectronic device comprising:
 a substrate; 
 a buffer layer located on the substrate, wherein the buffer layer is formed of a group III nitride material including aluminuman AlN buffer layer located on the substrate; 
 a first superlattice structure located on the buffer layer, wherein the first superlattice structure is formed of a plurality of periods, each period including two layers formed of group III nitride materials including aluminum and having molar fractions x and x′ an Al x Ga 1-x N layer and an Al x′ Ga 1-x′ N layer, where x>x′; 
 a second superlattice structure located on the first superlattice structure, wherein the second superlattice structure is formed of a plurality of periods, each period including two layers formed of group III nitride materials including aluminum and having molar fractions y and y′ an Al y Ga 1-y N layer and an Al y′ Ga 1-y′ N layer, where y>y′; 
 a n-type layer located on the second superlattice, wherein the n-type layer is formed of a group III nitride material including aluminum having a molar fraction z, Al z Ga 1-z N and wherein 0.1<z≤0.9; and 
 an active structure including quantum wells and barriers located on the n-type layer, wherein the quantum wells are formed of a group III nitride material including aluminum having a molar fraction q Al b Ga 1-b N and the barriers are formed of a group III nitride material including aluminum having a molar fraction b, Al q Ga 1-q N and wherein b-q>0.05. 
 
     
     
       20. The optoelectronic device of  claim 19 , further comprising an electron blocking layer located on the active structure, wherein the electron blocking layer is formed of a group III nitride material including aluminum having a molar fraction B, and wherein B is at least 1.05*b. 
     
     
       21. The optoelectronic device of claim 19, further comprising a grading structure located between the second superlattice structure and the n-type layer, wherein the grading structure has an aluminum molar fraction that decreases from an aluminum molar fraction at a bottom heterointerface to an aluminum molar fraction at a top heterointerface.  
     
     
       22. The optoelectronic device of claim 21, wherein the grading structure located between the second superlattice structure and the n-type layer is a linear grading.  
     
     
       23. The optoelectronic device of claim 19, further comprising a p-type layer located on the electron blocking layer, and a graded p-type layer located between the electron blocking layer and the GaN layer, wherein the graded p-type layer has an aluminum molar fraction that decreases from the heterointerface between the electron blocking layer and the graded p-type layer to an aluminum molar fraction at a heterointerface between the graded p-type layer and the p-type layer.  
     
     
       24. The optoelectronic device of claim 23, wherein the graded p-type layer located between the electron blocking layer and the GaN layer is a linear grading.  
     
     
       25. The optoelectronic device of claim 19, wherein a dominant wavelength is within a range of wavelengths between approximately 210 and approximately 350 nanometers.  
     
     
       26. The optoelectronic device of claim 19, further comprising a buffer layer having a thickness greater than 0.1 microns and less than or equal to 100 microns.  
     
     
       27. The optoelectronic device of claim 19, further comprising a buffer layer comprising an AlGaN layer having an aluminum molar fraction between 0.7 and 1.  
     
     
       28. The optoelectronic device of claim 19, wherein the band gap of the quantum wells is lower than a bandgap of a target wavelength.  
     
     
       29. The optoelectronic device of claim 19, wherein the optoelectronic device has a flip chip arrangement.  
     
     
       30. The optoelectronic device of claim 19, further comprising a submount formed of aluminum nitride (AlN) or silicon carbide (SiC).  
     
     
       31. The optoelectronic device of claim 19, wherein the first superlattice structure includes between ten and one hundred periods.  
     
     
       32. The optoelectronic device of claim 19, the second superlattice structure includes between ten and one hundred periods.  
     
     
       33. The optoelectronic device of claim 19, wherein the active structure comprises alternating quantum well and barrier layers, the barrier layers in the active structure have a thicknesses in a range of 5 nanometers to 25 nanometers, and the quantum well layers in the active structure have a thicknesses in a range of 1 nanometers to 5 nanometers.  
     
     
       34. The optoelectronic device of claim 19, wherein the active structure is configured to emit electromagnetic radiation having a peak emission wavelength between 260 nanometers and 300 nanometers, and wherein 0.6<x′<0.9, 0.5<y′<0.8, 0.4<z<0.75, and 0.2<q<0.6.  
     
     
       35. The optoelectronic device of claim 19, wherein the active structure is configured to emit electromagnetic radiation having a peak emission wavelength between 300 nanometers and 360 nanometers, and wherein 0.25<z<0.5; 0.45<y′<0.65; and 0.6<x′<0.8, where z<y′<x′.  
     
     
       36. The optoelectronic device of claim 19, wherein the active structure is configured to emit electromagnetic radiation having a peak emission wavelength between 300 nanometers and 360 nanometers, and wherein 0.05<z<0.5; 0.1<y′<0.4; and 0.1<x′<0.4.  
     
     
       37. The optoelectronic device of claim 19, wherein the active structure is configured to emit electromagnetic radiation having a peak emission wavelength between 300 nanometers and 360 nanometers, wherein the n-type layer includes sublayers, and wherein each sublayer differs from an immediately adjacent sublayer by at least one of: doping concentration or aluminum molar fraction.  
     
     
       38. The optoelectronic device of claim 19, wherein the active structure is configured to emit electromagnetic radiation having a peak emission wavelength between 260 nanometers and 300 nanometers, wherein the n-type layer includes sublayers, and wherein each sublayer differs from an immediately adjacent sublayer by at least one of: doping concentration or aluminum molar fraction.