Injection incoherent emitter

• US 6,429,462 B1
• Filed: 12/29/1999
• Issued: 08/06/2002
• Est. Priority Date: 12/29/1998
• Status: Expired due to Fees

• Current Assignee: D-Led Corporation
• Original Assignee: D-Led Corporation
• Inventors: Shveykin, Vasily I.
• Primary Examiner(s): Tran, Minh Loan
• Application Number:
  US09/474,744
• Time in Patent Office: 951 Days
• Field of Search: 257/94, 257/95, 257/96, 257/98, 257/101, 257/103, 257/13, 257/79
• US Class Current: 257/95
• CPC Class Codes: H01L 21/24 Alloying of impurity materials, e.g. doping materials, electrode materials, with a semiconductor body H01L21/182 takes precedence
• CPC Class Codes: H01L 2224/48247 connecting the wire to a bond pad of the item
• CPC Class Codes: H01L 27/156 two-dimensional arrays
• CPC Class Codes: H01L 2924/00012 Relevant to the scope of the group, the symbol of which is combined with the symbol of this group
• CPC Class Codes: H01L 2924/181 Encapsulation
• CPC Class Codes: H01L 33/0045 the devices being superluminescent diodes
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/405 Reflective materials
• CPC Class Codes: H01L 33/46 Reflective coating, e.g. dielectric Bragg reflector

Abstract

An injection incoherent emitter outputs a directed beam of light resulting from spontaneous emission. The emitter provides small divergence angles and enhanced external efficiency, as well as increased energy and light power. Specific ranges of compositions and thicknesses for layers and sublayers in the entire heterostructure, as well as for the layers of the emission output area may be employed to create this emitter. Different embodiments for the heterostructure and output areas permit emission from the emitters in different but controllable directions. One such direction is perpendicular to the active layer. Other embodiments include multibeam incoherent emitters, including embodiments that emit from lines and arrays of emitters, wherein each emitter has an independently controllable beam.

Claims

1. An injection incoherent emitter comprising:

a heterostructure comprising;

at least one active layer;

cladding layers; and

ohmic contacts, and

at least one emission output area on at least one side of the active layer, the emission output area adjoining at least one of the cladding layers, the emission output area being transparent for emission, the emission output area comprising at least one emission output area layer having a refractive index n_oaq, where q=1, 2, . . . p is defined as a whole number that designates the ordinal number of the emission output area layer enumerated from a boundary of the emission output area with the heterostructure, the emission output area and the heterostructure together having an effective refractive index n_ef, the effective refractive index n_ef of the heterostructure and the emission output area and the refractive index n_oa1 of the emission output area being selected to satisfy the correlations;

2. The injection incoherent emitter as defined in claim 1, wherein the active layer of the heterostructure comprises at least one sublayer.

3. The injection incoherent emitter as defined in claim 1, wherein a first cladding layer is located on a first surface of the active layer and a second cladding layer is located on a second surface of the active layer, the first cladding layer comprising a plurality of cladding sublayers I_i where i=1, 2, . . . k, the second cladding layer comprising a plurality of cladding sublayers II_j, where j=1, 2, . . . m, where i and j are defined as whole numbers that designate the ordinal number of respective cladding sublayers enumerated from the active layer, the cladding sublayers having respective refractive indices n_Ii and n_IIj.

4. The injection incoherent emitter as defined in claim 3, wherein at least one heterostructure cladding layer is formed as a gradient.

5. The injection incoherent emitter as defined in claim 1, wherein the heterostructure comprises at least one injection area.

6. The injection incoherent emitter as defined in claim 5, wherein:

the injection area has dimensions and an area S_ia and the emission output area has a surface adjoining a boundary layer of the heterostructure with dimensions and an area S_is; and

the dimensions and area S_ia of the injection area do not exceed the dimensions and area S_is of the emission output area surface adjoining the boundary layer of the heterostructure.

7. The injection incoherent emitter as defined in claim 1, wherein each cladding layer has a respective thickness, the thickness of the cladding layer adjoining the emission output area being less than the thickness of the cladding layer located on the opposite side of the active layer.

8. The injection incoherent emitter as defined in claim 1, wherein each cladding layer has a respective refractive index, the refractive index of the cladding sublayer adjoining the emission output area being greater than the refractive index of the cladding sublayer located on the opposite side of the active layer.

9. The injection incoherent emitter as defined in claim 1, wherein the emission output area layer has a thickness d_oaq in the range 1 μ

m to 10,000 μ

m.

10. The injection incoherent emitter as defined in claim 1, wherein the emission output area is conducting.

11. The injection incoherent emitter as defined in claim 10, wherein:

the emission output area has an internal surface and at least one outer surface opposite the internal surface; and

ohmic contact is formed to the at least one outer surface of the emission output area.

12. The injection incoherent emitter as defined in claim 1, wherein the emission output area comprises optically homogeneous material.

13. The injection incoherent emitter as defined in claim 1, wherein:

the emission output area comprises at least a first layer and a second layer;

the first layer borders the heterostructure, conducts, and comprises a material having an optical loss factor α

_oa1; and

the second layer comprises material that has an optical loss factor α

_oa2 that is lower than the optical loss factor α

_oa1 for the first layer.

14. The injection incoherent emitter as defined in claim 13, wherein the second layer is insulating.

15. The injection incoherent emitter as defined in claim 14, wherein:

the heterostructure includes at least two neighboring injection areas, the neighboring injection areas being electrically separated at least to the insulating second layer of the emission output area; and

the neighboring injection areas include ohmic contacts that are electrically connected by a metal coating layer.

16. The injection incoherent emitter as defined in claim 13, wherein the first layer has a refractive index n_oa1 and the second layer has a refractive index n_oa2, the refractive index n_oa2 of the second layer being smaller than the refractive index n_oa1 of the first layer.

17. The injection incoherent emitter as defined in claim 1, wherein at least one layer of the emission output area comprises a semiconductor.

18. The injection incoherent emitter as defined in claim 1, wherein at least one layer of the emission output area comprises a substrate material.

19. The injection incoherent emitter as defined in claim 1, wherein an ohmic contact is made to a first emission output area layer, said layer being conductive.

20. The injection incoherent emitter as defined in claim 1, wherein the emission output area comprises at least one truncated right cone, the cone having at least one base located on the cladding sublayer adjoining the emission output area.

21. The injection incoherent emitter as defined in claim 20, wherein:

the truncated right cone of the emission output area has a side surface and an inner surface;

the side surface is generated by a generatrix having a linear slope angle ψ

with respect to the inner surface, the angle ψ

selected to be in the range (π

/2−

φ

−

σ

) to (π

/2−

φ

+σ

), wherein;

φ

is an angle between a plane defined by the active layer and a perpendicular to an emission front propagating in the emission output area; and

σ

is an angle of total internal reflection from the side surface for emission propagating in the emission output region.

22. The injection incoherent emitter as defined in claim 20, wherein:

the truncated right cone of the emission output area has a side surface and an inner surface;

the side surface is generated by a generatrix having a linear slope angle ψ

with respect to the inner surface, the angle ψ

selected to be in the range (3π

/4−

φ

/2−

σ

/2) to (3π

/4−

φ

/2+σ

/2), wherein;

φ

is an angle between a plane defined by the active layer and a perpendicular to an emission front propagating in the emission output area; and

σ

is an angle of total internal reflection from the side surface for emission propagating in the emission output region.

23. The injection incoherent emitter as defined in claim 20, wherein:

the truncated right cone of the emission output area has a side surface and an inner surface;

the side surface is generated by a generatrix having a linear slope angle ψ

with respect to the inner surface, the angle ψ

selected to be in the range (π

/4−

φ

/2−

σ

/2) to (π

/4−

φ

/2+σ

/2), wherein;

φ

is an angle between a plane defined by the active layer and a perpendicular to an emission front propagating in the emission output area; and

σ

is an angle of total internal reflection from the side surface for emission propagating in the emission output region.

24. The injection incoherent emitter as defined in claim 1, wherein the emission output area is formed as at least one right circular cylinder, the cylinder having a base located on the cladding layer adjoining the emission output area.

25. The injection incoherent emitter as defined in claim 1, wherein the emission output area is formed as at least one hexahedron, the hexahedron having a base located on the cladding layer adjoining the emission output area.

26. The injection incoherent emitter as defined in claim 25, wherein:

the at least one hexahedron has at least one side surface and an inner surface, the side surface having a linear slope angle ψ

with respect to the inner surface is selected from a range of (π

/2−

φ

−

Δ

φ

/2) to (π

/2−

φ

+Δ

φ

/2);

φ

is a propagation angle between a plane defined by the active layer and a perpendicular to an emission front propagating in the emission output area; and

Δ

φ

is an emission divergence angle in a vertical plane.

27. The injection incoherent emitter as defined in claim 25, wherein:

the at least one hexahedron has at least one side surface and an inner surface, the side surface having a linear slope angle ψ

with respect to the inner surface is selected from a range of (3π

/4−

φ

/2−

Δ

φ

/2) to (3π

/4−

φ

/2+Δ

φ

/2);

φ

is a propagation angle between a plane defined by the active layer and a perpendicular to an emission front propagating in the emission output area; and

Δ

φ

is an emission divergence angle in a vertical plane.

28. The injection incoherent emitter as defined in claim 25, wherein:

the at least one hexahedron has at least one side surface and an inner surface, the side surface having a linear slope angle ψ

with respect to the inner surface is selected from a range of (π

/4−

φ

/2−

Δ

φ

/2) to (π

/4−

φ

/2+Δ

φ

/2);

φ

is a propagation angle between a plane defined by the active layer and a perpendicular to an emission front propagating in the emission output area; and

Δ

φ

is an emission divergence angle in a vertical plane.

29. The injection incoherent emitter as defined in claim 25, wherein the at least one hexahedron has at least one side surface and an inner surface, the side surface having a linear slope angle ψ

with respect to the inner surface of π

/2.

30. The injection incoherent emitter as defined in claim 1, wherein:

φ

is an angle between a plane defined by the active layer and a perpendicular to an emission front propagating in the emission output area; and

σ

is an angle of total internal reflection from a side surface of the emission output area for emission propagating in the emission output region, the angle of total reflection σ

being greater than the propagation angle φ

.

31. The injection incoherent emitter as defined in claim 1, wherein the emission output area has at least one output surface, at least a portion of the at least one output surface having an antireflection coating thereon.

32. The injection incoherent emitter as defined in claim 1, wherein the emission output area has at least one output surface, at least a portion of the at least one output surface having a reflection coating thereon.

33. The injection incoherent emitter as defined in claim 1, wherein the heterostructure comprises at least two injection areas, each injection area having a propagation angle, the propagation angles of the injection areas being the equal.

34. The injection incoherent emitter as defined in claim 33, wherein an independent ohmic contact is made to each injection area from an external side of the heterostructure.

35. The injection incoherent emitter as defined in claim 33, wherein each injection area is associated with one of the at least one emission output areas.

36. The injection incoherent emitter as defined in claim 35, wherein at least two of the injection areas are associated with a common one of the at least one emission output areas.

37. The injection incoherent emitter as defined in claim 1, wherein the heterostructure comprises a plurality of injection areas having equal dimensions, the injection areas being arranged along a line as a linear sequence of injection areas.

38. The injection incoherent emitter as defined in claim 37, wherein the plurality of injection areas are electrically connected by a metal coating layer formed in at least one band.

39. The injection incoherent emitter as defined in claim 38, wherein the heterostructure comprises at least two linear sequences of injection areas, the plurality of injection areas in each linear sequence being connected by a respective band.

40. The injection incoherent emitter as defined in claim 39, further comprising a band which electrically connects one injection area from each of the linear sequences.

41. The injection incoherent emitter as defined in claim 1, wherein each injection area is bounded by injected barrier layers.