Application of semiconductor quantum dot phosphors in nanopillar light emitting diodes
A quantum well-based p-i-n light emitting diode is provided that includes nanopillars with an average linear dimension of between 50 nanometers and 1 micron. The nanopillars include a laminar layer of quantum wells capable of non-radiative energy transfer to quantum dot nanocrystals. Quantum dot-Quantum well coupling through the side walls of the nanopillar-configured LED structure achieves a close proximity between quantum wells and quantum dots while retaining the overlying contact electrode structures. A white LED with attractive properties relative to conventional incandescent and fluorescence lighting devices is produced.
1. A quantum well-based p-i-n light emitting diode comprising:
a substrate;
a first ohmic contact layer directly or indirectly layered on said substrate;
a first electrode in electrical communication with said first ohmic contact;
an n-type or p-type layer on said ohmic contact layer;
a plurality of nanopillars that have a mean nanopillar average linear dimension of between 50 nanometers and 1 micron and each of said plurality of nanopillars having a height, each of said plurality of nanopillars defined by a sidewall, at least one laminar semiconductor quantum well having a quantum well band gap existing along the height intermediate between an said n-type or p-type layer and an oppositely doped layer to said n-type or p-type layer;
a plurality of non-homogeneous core-shell quantum dot semiconductor nanoparticles contacting the sidewall proximal to the at least one laminar semiconductor quantum well, said non-homogeneous core-shell plurality of quantum dot semiconductor nanoparticles having band gaps that are less than or equal to the quantum well bandgap and vary in size and a relative thickness of core-shell layers;
a second ohmic contact layer directly or indirectly in electrical contact with said oppositely doped layer; and
a second electrode in electrical communication with said second ohmic contact and forming an electrical circuit with said first electrode.
2. The diode of claim 1 wherein said plurality of nanopillars are right cylinders.
3. The diode of claim 1 wherein said plurality of non-homogeneous core-shell quantum dot semiconductor nanocrystals comprise a II-VI semiconductor.
4. The diode of claim 1 wherein said plurality of non-homogeneous core-shell quantum dot semiconductor nanocrystals comprise core-shell nanocrystals with cadmium selenide cores with cadmium sulfide shells.
5. The diode of claim 1 wherein said plurality of nanopillars are etched through said at least one quantum well and said oppositely doped layer and said n-type or p-type layer.
6. The diode of claim 1 further comprising an intermediate layer in simultaneous contact between said first ohmic contact layer and said substrate.
7. The diode of claim 1 further comprising a power source having a voltage to induce spectral emission from said at least one quantum well.
8. The diode of claim 1 wherein said n-type or p-type layer is n-type and said oppositely doped layer is p-type.
9. The diode of claim 1 wherein the band gaps of said plurality of non-homogeneous core-shell quantum dot semiconductor nanocrystals collectively provide an emission discerned by a normal human eye as white in color.
10. The diode of claim 1 wherein the at least one laminar semiconductor quantum well is a plurality of quantum wells that are vertical displaced along the height of one of said plurality of nanopillars.
11. A light emitting diode comprising:
a substrate;
a first ohmic contact layer of n+ GaN directly or indirectly layered on said substrate;
a first n-type electrode in electrical communication with said first ohmic contact;
an n-type n-doped GaN layer on said ohmic contact layer;
a plurality of nanopillars that have a mean nanopillar average linear dimension of between 50 nanometers and 1 micron and each of said plurality of nanopillars having a height, each of said plurality of nanopillars defined by a sidewall, at least one InGaN quantum well existing along the height intermediate between an said n-type n-doped GaN layer and a p-type p-doped GaN doped layer;
a plurality of non-homogeneous core-shell quantum dot semiconductor nanoparticles contacting the sidewall proximal to the InGaN quantum well, said plurality of non-homogeneous core-shell quantum dot semiconductor nanoparticles having band gaps that are less than a band gap for the at least one InGaN quantum and vary in size and a relative thickness of core-shell layers;
a second ohmic contact layer of p+ GaN directly or indirectly in electrical contact with said p-type p-doped GaN doped layer; and
a second electrode in electrical communication with said second ohmic contact and forming an electrical circuit with said first electrode.
12. The diode of claim 11 wherein said plurality of nanopillars are right cylinders.
13. The diode of claim 11 wherein said plurality of non-homogeneous core-shell quantum dot semiconductor nanocrystals comprise a II-VI semiconductor.
14. The diode of claim 11 wherein said plurality of non-homogeneous core-shell quantum dot semiconductor nanocrystals comprise core-shell nanocrystals with cadmium selenide cores with cadmium sulfide shells.
15. The diode of claim 11 wherein said plurality of nanopillars are etched through said at least InGaN quantum well and into said n-type n-doped GaN layer.
16. The diode of claim 11 further comprising an intermediate layer in simultaneous contact between said first ohmic contact layer of n+ GaN and said substrate.
17. The diode of claim 11 further comprising a power source having a voltage to induce spectral emission from said at least one quantum well.
18. The diode of claim 11 wherein the band gaps of said plurality of non-homogeneous core-shell quantum dot semiconductor nanocrystals collectively provide an emission discerned by a normal human eye as white in color.
19. The diode of claim 11 wherein the at least one laminar semiconductor quantum well is a plurality of quantum wells that are vertical displaced along the height of one of said plurality of nanopillars.