Amber light-emitting diode comprising a group III-nitride nanowire active region
A temperature stable (color and efficiency) III-nitride based amber (585 nm) light-emitting diode is based on a novel hybrid nanowire-planar structure. The arrays of GaN nanowires enable radial InGaN/GaN quantum well LED structures with high indium content and high material quality. The high efficiency and temperature stable direct yellow and red phosphor-free emitters enable high efficiency white LEDs based on the RGYB color-mixing approach.
1. A light-emitting diode, comprising:
a substrate having a frontside and a backside;
an n-type base grown on the frontside of the substrate;
a core-shell structure on the n-type base, comprising an array of vertically aligned faceted n-type nanowire cores, each core surrounded by a radially grown Group III-nitride multiple quantum well shell layer providing a core-shell nanowire;
a p-type canopy layer grown on all crystal facets of the core-shell nanowires, and that is coalesced at the top providing a continuous top surface, wherein the top surface of the canopy layer is faceted on a plurality of crystal planes of the nanowire cores, thereby providing a continuous film that electrically connects the tops and sides of all the nanowires, further providing a void between adjacent n-type nanowire cores and between the continuous top surface and the n-type base; and
a p-contact to the p-type canopy layer and an n-contact to the n-type base for applying a voltage across the core-shell structure and extracting electroluminescent emitted light therefrom.
2. The light-emitting diode of claim 1 , wherein the n-type nanowire cores comprise n-type GaN, the shell layer comprises an InGaN/GaN multiple quantum well, and the p-type canopy layer comprises p-type InGaN or p-type GaN.
3. The light-emitting diode of claim 2 , wherein the indium concentration of the InGaN layers of the multiple quantum well is greater than 20%.
4. The light-emitting diode of claim 1 , wherein the emitted light has a wavelength of between 550 nm and 620 nm.
5. The light-emitting diode of claim 1 , wherein the p-contact comprises Ni/Au, a transparent conductive oxide, or Ag.
6. The light-emitting diode of claim 1 , wherein the n-contact comprises Al or Ti/Au.
7. The light-emitting diode of claim 1 , wherein the substrate is transparent to the emitted light.
8. The light-emitting diode of claim 7 , wherein the substrate comprises sapphire, silicon, GaN, SiC, or AIN.
9. The light-emitting diode of claim 7 , further comprising a reflective layer deposited on the backside of the substrate.
10. The light-emitting diode of claim 9 , wherein the reflective layer comprises aluminum or silver.
11. The light-emitting diode of claim 1 , further comprising a spreading metal contact layer on the p-type canopy layer.
12. The light-emitting diode of claim 1 , further comprising an indium-tin-oxide layer on the p-type canopy layer.
13. The light-emitting diode of claim 2 , further comprising an InGaN underlayer between the n-type nanowire core and the InGaN/GaN multiple quantum well shell layer.
14. The light-emitting diode of claim 2 , further comprising an AlGaN electron blocking layer between the InGaN/GaN multiple quantum well shell layer and the p-type canopy layer.
15. The light-emitting diode of claim 1 , wherein the height of the nanowire cores is less than 10 microns.
16. The light-emitting diode of claim 1 , wherein the diameter of the nanowire cores is less than 1 micron.
17. The light-emitting diode of claim 1 , wherein the array comprises a hexagonal or rectangular lattice.