Nitride-based light emitting heterostructure

• US 7,326,963 B2
• Filed: 12/02/2005
• Issued: 02/05/2008
• Est. Priority Date: 12/06/2004
• Status: Active Grant

• Current Assignee: Sensor Electronic Technology Incorporated (Seoul Semiconductor Co., Ltd.)
• Original Assignee: Sensor Electronic Technology Incorporated (Seoul Semiconductor Co., Ltd.)
• Inventors: Shur, Michael, Gaska, Remigijus, Zhang, Jianping
• Primary Examiner(s): Pham; Long
• Application Number:
  US11/292,519
• Publication Number:
  US 20060118820A1
• Time in Patent Office: 795 Days
• Field of Search: 257/79
• US Class Current: 257/79
• CPC Class Codes: B82Y 20/00 Nanooptics, e.g. quantum optics or photonic crystals
• CPC Class Codes: H01L 33/06 within the light emitting region, e.g. quantum confinement structure or tunnel barrier
• CPC Class Codes: H01L 33/32 containing nitrogen
• CPC Class Codes: H01S 5/11 Comprising a photonic bandgap structure
• CPC Class Codes: H01S 5/2009 by using electron barrier layers
• CPC Class Codes: H01S 5/3216 quantum well or superlattice cladding layers
• CPC Class Codes: H01S 5/3407 characterised by special barrier layers
• CPC Class Codes: H01S 5/3415 containing details related to carrier capture times into wells or barriers
• CPC Class Codes: H01S 5/34333 with a well layer based on Ga(In)N or Ga(In)P, e.g. blue laser
• CPC Class Codes: H01S 5/34346 characterised by the materials of the barrier layers

Abstract

An improved nitride-based light emitting heterostructure is provided. The nitride-based light emitting heterostructure includes an electron supply layer and a hole supply layer with a light generating structure disposed there between. The light generating structure includes a set of barrier layers, each of which has a graded composition and a set of quantum wells, each of which adjoins at least one barrier layer. Additional features, such as a thickness of each quantum well, can be selected/incorporated into the heterostructure to improve one or more of its characteristics. Further, one or more additional layers that include a graded composition can be included in the heterostructure outside of the light generating structure. The graded composition layer(s) cause electrons to lose energy prior to entering a quantum well in the light generating structure, which enables the electrons to recombine with holes more efficiently in the quantum well.

Claims

1. A nitride-based light emitting heterostructure comprising:

an electron supply layer;

a hole supply layer; and

a light generating structure disposed between the electron supply layer and the hole supply layer, the light generating structure including;

a set of barrier layers, each barrier layer comprising a graded composition; and

a set of quantum wells, each quantum well adjoined by a barrier layer and having a thickness less than a characteristic radius of a defect responsible for nonradiative recombination, wherein the graded composition of each barrier layer causes electrons to lose energy prior to entering a quantum well.

2. The nitride-based light emitting heterostructure of claim 1, wherein a thickness of each quantum well is such that an electron ground state of each quantum well is above a band bending range of energies caused by a set of polarization effects.

3. The nitride-based light emitting heterostructure of claim 1, each barrier layer comprising one of an AlGaN or an AlGaInN composition.

4. The nitride-based light emitting heterostructure of claim 1, further comprising an electron blocking layer disposed between the light generating structure and the hole supply layer.

5. The nitride-based light emitting heterostructure of claim 4, wherein the electron blocking layer comprises a graded composition that transitions from a hole supply layer composition to an electron blocking layer composition.

6. The nitride-based light emitting heterostructure of claim 1, wherein the hole supply layer comprises a graded composition that transitions from a hole supply layer composition to an electron blocking layer composition closer to the light generating structure.

7. The nitride-based light emitting heterostructure of claim 1, further comprising:

a substrate;

a buffer layer on the substrate; and

a strain-relieving structure over the buffer layer.

8. The nitride-based light emitting heterostructure of claim 1, wherein the electron supply layer comprises an n-type contact layer and wherein the hole supply layer comprises a p-type contact layer.

9. The nitride-based light emitting heterostructure of claim 1, further comprising at least one barrier layer adjacent to the electron supply layer, the at least one barrier layer comprising a graded composition that creates a band structure profile such that electrons entering the light generating structure have an energy that is approximately the same as an energy of a polar optical phonon.

10. The nitride-based light emitting heterostructure of claim 1, further comprising at least one barrier layer adjacent to the hole supply layer, the at least one barrier layer comprising a graded composition that creates a band structure profile such that holes entering the light generating structure have an energy that is approximately the same as an energy of a polar optical phonon.

11. The nitride-based light emitting heterostructure of claim 1, wherein the hole supply layer comprises a doped short period superlattice.

12. The nitride-based light emitting heterostructure of claim 1, further comprising a p-type layer disposed between the light generating structure and the hole supply layer.

13. The nitride-based light emitting heterostructure of claim 1, further comprising a Distributive Bragg Reflector (DBR) structure disposed over the light generating structure.

14. The nitride-based light emitting heterostructure of claim 13, wherein the DBR structure comprises a doped p-type composition.

15. The nitride-based light emitting heterostructure of claim 1, further comprising an anodized aluminum layer disposed over the hole supply layer.

16. The nitride-based light emitting heterostructure of claim 15, wherein the hole supply layer and the anodized aluminum layer comprise a plurality of holes that form a photonic crystal.

17. The nitride-based light emitting heterostructure of claim 15, wherein the hole supply layer includes a set of holes, each of which is aligned with a hole in the anodized aluminum layer.

18. The nitride-based light emitting heterostructure of claim 17, wherein at least one of the set of holes includes a material having a different refractive index than a composition of the p-type layer.

21. The nitride-based light emitting heterostructure of claim 1, wherein each barrier layer has a varying composition of Aluminum that increases a baffler for electrons and reduces a barrier for holes at a boundary with a quantum well as compared to a baffler layer having a constant composition of Aluminum.

19. A nitride-based light emitting device comprising:

a substrate;

a buffer layer on the substrate;

a strain-relieving structure over the buffer layer;

an electron supply layer over the strain-relieving structure;

a hole supply layer; and

a light generating structure disposed between the electron supply layer and the hole supply layer, the light generating structure including;

a set of barrier layers, each barrier layer comprising a graded composition; and

a set of quantum wells, each quantum well adjoined by a barrier layer and having a thickness less than a characteristic radius of at least one defect responsible for nonradiative recombination.

20. The nitride-based light emitting device of claim 19, configured to operate as one of a light emitting diode or a laser.