High efficiency light emitters with reduced polarization-induced charges
First Claim
1. An optical emitter, comprising:
- an n-type contact layer;
a p-type contact layer;
an active light emitting region sandwiched between cladding layers, said active region and cladding layers between said n-type and p-type contact layers;
dipoles across said active region, said dipoles formed from interfacial charge sheets along the interfaces between said active region and said cladding layers, said dipoles generating a polarization induced field across said active region that reduces the light emitting efficiency of said optical emitter; and
a means for at least decreasing some of the efficiency reducing effect of said polarization-induced field across said active region.
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Accused Products
Abstract
Naturally occurring polarization-induced electric fields in a semiconductor light emitter with crystal layers grown along a polar direction are reduced, canceled or reversed to improve the emitter'"'"'s operating efficiency and carrier confinement. This is accomplished by reducing differences in the material compositions of adjacent crystal layers, grading one or more layers to generate space charges and quasi-fields that oppose polarization-induced charges, incorporating various impurities into the semiconductor that ionize into a charge state opposite to the polarization induced charges, inverting the sequence of charged atomic layers, inverting the growth sequence of n- and p-type layers in the device, employing a multilayer emission system instead of a uniform active region and/or changing the in-plane lattice constant of the material.
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Citations
43 Claims
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1. An optical emitter, comprising:
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an n-type contact layer;
a p-type contact layer;
an active light emitting region sandwiched between cladding layers, said active region and cladding layers between said n-type and p-type contact layers;
dipoles across said active region, said dipoles formed from interfacial charge sheets along the interfaces between said active region and said cladding layers, said dipoles generating a polarization induced field across said active region that reduces the light emitting efficiency of said optical emitter; and
a means for at least decreasing some of the efficiency reducing effect of said polarization-induced field across said active region. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
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21. An optical emitter grown along a crystal polar direction, comprising:
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a plurality of crystal layers whose material compositions vary in said polar direction, said plurality of layers comprising at least an active region sandwiched between two cladding layers, said varied composition generating oppositely charged interfacial charge sheets at the interfaces between said active region and cladding layer;
at least one of said cladding layers incorporating dopant impurities that ionize into a charged state opposite to the sheet charge at the interface between said doped cladding layer and said active region to cancel at least some of said sheet charge. - View Dependent Claims (22, 23)
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24. An optical emitter grown normal to a crystal polar direction, comprising:
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n- and p-type contact layers;
an active region sandwiched between two cladding layers, said active region and cladding layers between said n- and p-type contact layers;
interfacial sheet charges at the interfaces between said active region and cladding layers;
at least one of said cladding layers having an intermediate material composition relative to said active region and adjacent n- or p-type layer, said intermediate composition reducing the charge of the sheet charge adjacent to said doped cladding layer. - View Dependent Claims (25, 26)
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27. An optical emitter grown normal to a crystal polar direction, comprising:
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a plurality of crystal layers comprising at least an active region sandwiched between two cladding layers, said layers having material compositions that vary in said polar direction to generate a polarization-induced charge concentration in said active region;
said active layer comprised of a ternary compound material and at least one of said cladding layer comprised of a quaternary material that results in a reduced polarization induces charge concentration at the interface between said active region and said quaternary cladding layer. - View Dependent Claims (28)
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29. An optical emitter grown normal to a crystal polar direction, comprising:
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a plurality of crystal layers comprising at least an active region sandwiched between two cladding layers, said layers having material compositions that vary in said polar direction to generate a polarization-induced charge concentration in said active region;
at least one of said cladding layers having a composition that is graded to generate a space charge over a volume of said grade that opposes said charge concentration. - View Dependent Claims (30)
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31. An optical emitter grown along a crystal polar direction, comprising:
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a plurality of crystal layers, comprising at least an active region sandwiched between two cladding layers, said layers having material compositions that vary in said polar direction;
at least one of said layers having its composition graded to generate a space charge over a volume of said grade that allows dopant impurities to be set back from an adjacent layer. - View Dependent Claims (32)
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33. An optical emitter grown along a crystal polar direction, comprising:
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a plurality of crystal layers comprising at least an active region sandwiched between two cladding layer, said layers having material compositions that vary in said polar direction to generate a polarization-induced electric field in said active region;
said active region having a composition that is graded to generate a quasi-field that opposes said polarization-induced electric field. - View Dependent Claims (34, 35)
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36. An optical emitter grown along a crystal polar direction, comprising:
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at least one each of p-type and n-type crystal layers whose material compositions vary in said polar direction to generate a polarization-induced charge concentration in at least one of said layers the adversely effects the performance of said emitter;
a plurality of crystal layers between said p-type and n-type crystal layers, said plurality of layers including at least an active region sandwiched between two cladding layers;
said p-type layer preceding said n-type layer in growth sequence to reverse the effect of said charge concentration on said optical emitters performance.
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37. An optical emitter grown normal to a crystal polar direction, comprising:
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a plurality of crystal layers including at least an active region sandwiched between two cladding layers, said layers having compositions that vary in said polar direction to generate a polarization-induced electric fields in at least one of said layers;
one of said layers comprising a multilayer active region that comprises alternating optical emitting and non-emitting layers, with said non-emitting layers confining injected carriers in said emitting layers and opposing said electric fields. - View Dependent Claims (38, 39, 40, 41)
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42. An optical emitter grown normal to a crystal polar direction, comprising:
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a plurality of crystal layers whose material compositions vary in said polar direction to generate polarization-induced electric fields in at least one of said layers;
at least one of said layers being an active region;
at least a second one of said being below said active region and being at least partially strain-relaxed such that the in-plane lattice constant of said layer below said active region is close to the unstrained in-plane lattice constant of said active region, thus reducing, eliminating, or reversing said electric field in said active region.
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43. An optical emitter grown normal to a crystal polar direction, comprising:
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a plurality of crystal layers whose material compositions vary in said polar direction to generate polarization-induced electric fields in at least one of said layers;
at least one of said layers being an active region;
said active region grown thick enough so that the material in the active region is at least partially strain-relaxed, thereby reducing said electric field in at least said active region.
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Specification