Reflective mounting substrates for light emitting diodes
View Patent ↗A light emitting diode is disclosed that includes a light emitting active structure formed from the Group III nitride material system, a bonding structure supporting the Group III nitride active structure, and a mounting substrate supporting the bonding structure. The mounting substrate includes a material that reflects at least fifty percent of light having the frequencies emitted by the active structure.
1. A light emitting diode comprising:
a light emitting active structure formed from a Group III nitride material system;
a bonding structure; and
a mounting substrate,
a first ohmic contact to a p-type portion of said light emitting active structure; and a second ohmic contact to an n-type portion of said light emitting active structure,
said mounting substrate comprising a material such that a surface of the mounting substrate reflects at least fifty percent of light having the frequencies emitted by said active structure, wherein said bonding structure is between said Group III nitride light emitting active structure and said mounting substrate.
2. A light emitting diode according to claim 1 wherein said bonding structure is a metal bonding structure.
3. A light emitting diode according to claim 1 wherein said mounting substrate comprises a material that is other than a Group III nitride.
4. A light emitting diode according to claim 1 wherein the material of said mounting substrate has a higher reflectivity than silicon for the light having frequencies emitted by said active structure.
5. A light emitting diode according to claim 1 wherein said active structure comprises epitaxial layers from a Group III nitride material system.
6. A light emitting diode according to claim 1 wherein said active structure is selected from the group consisting of homojunctions, heterojunctions, single quantum wells, multiple quantum wells, and super lattice structures.
7. A light emitting diode according to claim 1 wherein said mounting substrate is selected from the group consisting of aluminum oxide, boron nitride, magnesium oxide, titanium dioxide, aluminum, other metals, porcelains, and other ceramics.
8. A light emitting diode according to claim 1 wherein said mounting substrate is insulating.
9. A light emitting diode according to claim 1 , wherein said mounting substrate is conductive, and further comprising a first ohmic contact to said conductive mounting substrate; and a second ohmic contact to said active structure.
10. A light emitting diode according to claim 1 wherein said mounting substrate is chemically stable, can withstand LED fabrication temperatures, is at least as mechanically strong as silicon, has a high fracture strength, has a high toughness, a high thermal conductivity, is rigid, will bond to said bonding structure, and is substantially nontoxic in the LED manufacturing context.
11. A light emitting diode according to claim 1 wherein said mounting substrate is physically and chemically stable at temperatures up to at least about 300° C.
12. A light emitting diode according to claim 1 wherein said active structure is selected from the group consisting of gallium nitride, indium gallium nitride, aluminum gallium nitride, and combinations thereof.
13. A light emitting diode according to claim 1 wherein said bonding structure is metal and includes gold, tin, platinum and/or nickel.
14. A light emitting diode according to claim 1 further comprising a lens and a phosphor and wherein said mounting substrate material reflects a substantial amount of the light emitted by said phosphor.
15. A light emitting diode according to claim 1 wherein said mounting substrate material reflects at least fifty percent of light having a wavelength of between about 350 and 700 nanometers.