Patterned reflective grids for LED arrays and displays
LED arrays comprise patterned reflective grids that enhance the contrast ratio between adjacent pixels or adjacent groups of pixels in the array. The pattern on the reflective grid may also improve adhesion between the reflective grid and one or more layers of material disposed on and attached to the reflective grid. The reflective grid may be formed, for example, as a reflective metal grid, a grid of dielectric reflectors, or a grid of distributed Bragg reflectors (DBRs). If formed as a metal grid, the reflective grid may provide electrical contact to one side of the LED diode junctions. This specification also discloses fabrication processes for such LED arrays.
1. A light emitting diode array comprising:
a plurality of light emitting diodes each comprising a light emitting surface and a bottom diode surface opposite the light emitting surface, the light emitting surface comprising a pattern with features that comprise doped semiconductor material; and
a reflective grid defining a plurality of openings in which corresponding ones of the light emitting diodes are disposed with their light emitting surfaces facing in a same direction out of the reflective grid, the reflective grid providing reflective side walls for each light emitting diode, the reflective side walls comprising patterned light scattering surfaces arranged adjacent to the light emitting surfaces and facing in the same direction as the light emitting surfaces.
2. The light emitting diode array of claim 1 , wherein the features consist of n-type semiconductor material.
3. The light emitting diode array of claim 1 , wherein the features of the pattern of the light emitting surface and second features of the patterned light scattering surfaces have at least one of different shapes, size, or spacing from each other.
4. The light emitting diode array of claim 2 , wherein the features of the pattern of the light emitting surface and second features of the patterned light scattering surfaces comprise a different material from each other.
5. The light emitting diode array of claim 1 , wherein the patterned light scattering surfaces are coplanar with adjacent light emitting surfaces.
6. The light emitting diode array of claim 1 , wherein an entirety of the patterned light scattering surfaces extend beyond the light emitting surfaces in the direction in which the light emitting surfaces are facing.
7. The light emitting diode array of claim 1 , wherein the reflective grid is or comprises a reflective metal grid that provides electrical contact to the light emitting diodes.
8. The light emitting diode array of claim 1 , comprising a wavelength converting structure disposed on the light emitting surfaces and the patterned light scattering surfaces.
9. The light emitting diode array of claim 1 , wherein the patterned light scattering surfaces of the reflective grid consist of a same one or more materials as the reflective side walls of the reflective grid.
10. The light emitting diode array of claim 9 , comprising a wavelength converting structure disposed on the light emitting surfaces and the patterned light scattering surfaces, wherein:
the light emitting surfaces are patterned to scatter light;
the wavelength converting structure has a thickness of less than about 30 microns in the direction in which the light emitting surfaces face; and
the wavelength converting structure comprises phosphor particles dispersed in a binder, the phosphor particles having diameters less than about 20 microns and larger than 1 micron.
11. A display system comprising:
the light emitting diode array of claim 1 ;
a display; and
a lens or lens system spaced apart from the light emitting diode array and arranged to couple light from the light emitting diode array into the display.
12. The light emitting diode array of claim 1 , wherein the light emitting diodes comprise a doped semiconductor region and an active layer in direct contact with the doped semiconductor region, wherein the doped semiconductor region is continuous with the features of the pattern of the light emitting surface.