Pixilated display device based upon nanowire LEDs and method for making the same
A pixelated display device and a method for making the same are disclosed. The device may include an array of nanowire LEDs located above a substrate. When the nanowire LEDs are initially grown, they may emit first-wavelength light proximally to the substrate and second-wavelength light distally from the substrate. The nanowires may remain as initially grown, in which case only second-wavelength light is visible, or the second-wavelength light emitting portions may be etched away such that only first-wavelength light is visible.
1. A method of forming a pixilated display device, comprising:
growing an array of nanowire LEDs on a substrate, each nanowire LED in the array including a vertical stack, from bottom to top, of a first-wavelength light emitting portion including a first material emitting a first-wavelength light and a second-wavelength light emitting portion including a second material emitting a second-wavelength light; and
while masking a first nanowire LED within the array with a patterned masking layer, removing a second-wavelength light emitting portion from a second nanowire LED within the array;
wherein growing the array of nanowire LEDs on the substrate comprises:
forming a growth mask over the substrate, the growth mask having a first aperture in a first area of the first nanowire LED and a second aperture in a second area of the second nanowire LED;
forming a first nanowire core through the first aperture; and
forming a second nanowire core through the second aperture:
wherein:
the first nanowire LED comprises a core-shell nanowire device that comprises the first nanowire core and a first quantum well shell comprising the first-wavelength light emitting portion, the second-wavelength light emitting portion, and a first pyramidal plane quantum well;
the second nanowire LED comprises a core-shell nanowire device that comprises the second nanowire core and a second quantum well shell comprising the first-wavelength light emitting portion, the second-wavelength light emitting portion, and a second pyramidal plane quantum well;
the first quantum well shell is formed by deposition of an InGaN layer and a GaN layer around the first nanowire core;
the second quantum well shell is formed by deposition of the InGaN layer and the GaN layer around the second nanowire core;
the first quantum well shell and the second quantum well shell are deposited during the same deposition steps;
the first-wavelength light emitting portion of the first nanowire LED comprises a lower portion of the first quantum well shell located over m-plane sidewalls of the first nanowire core;
the second-wavelength light emitting portion of the first nanowire LED comprises an eave region of the first quantum well shell located between the lower portion of the first quantum well shell and the first pyramidal plane quantum well of the first quantum well shell located over pyramidal p-plane sidewalls of the first nanowire core;
the first-wavelength light emitting portion of the second nanowire LED comprises a lower portion of the second quantum well shell located over m-plane sidewalls of the second nanowire core; and
the second-wavelength light emitting portion of the second nanowire LED comprises an eave region of the second quantum well shell located between the lower portion of the second quantum well shell and the second pyramidal plane quantum well of the second quantum well shell located over pyramidal p-plane sidewalls of the second nanowire core.
2. The method of claim 1 , wherein:
the InGaN layer in the cave region of the first quantum well shell has at least 5 atomic percent higher indium content than the InGaN layer in the lower portion of the first quantum well shell, such that the first-wavelength light emitting portion of the first nanowire LED emits blue light and the second-wavelength light emitting portion of the second nanowire LED emits green light;
the InGaN layer in the eave region of the second quantum well shell has at least 5 atomic percent higher indium content than the InGaN layer in the lower portion of the second quantum well shell; and
removing the second-wavelength light emitting portion from a second nanowire LED within the array comprises removing the eave region of the second quantum well shell of the second nanowire LED while masking the first quantum well shell of the first nanowire LED.
3. The method of claim 2 , wherein:
the eave region and the lower portion of the first quantum well shell are not removed from the first nanowire LED during the step of removing the second-wavelength light emitting portion from the second nanowire LED;
the lower portion of the second quantum well shell is not removed from the second nanowire LED during the step of removing the second-wavelength light emitting portion from the second nanowire LED;
the first nanowire LED emits green light; and
the second nanowire LED emits blue light.
4. The method of claim 3 , wherein:
the first nanowire LED is located in a green light emitting subpixel of a display device; and
the second nanowire LED is located in a blue light emitting subpixel of the display device.
5. The method of claim 4 , further comprising providing a red light emitting subpixel of the display device to form a red, green and blue light emitting pixel of the display device.
6. The method of claim 5 , wherein the display device comprises a direct view display device.