LED USING LUMINESCENT SAPPHIRE AS DOWN-CONVERTER
An LED die includes a luminescent sapphire layer affixed to LED semiconductor layers. The luminescent sapphire absorbs a portion of the primary light and down-converts the primary light to emit secondary light. A phosphor layer may be added. The luminescent sapphire may comprise luminescent sapphire particles in a binder forming a mixture deposited over the LED semiconductor layers. Alternatively, the luminescent sapphire comprises a pre-formed tile that is affixed over the LED semiconductor layers. Alternatively, the luminescent sapphire comprises a luminescent sapphire growth substrate on which is epitaxially grown the LED semiconductor layers. After the LED die is formed, the luminescent characteristics of the sapphire maybe adjusted using optical conditioning and/or annealing to tune the die's overall emission.
1 . A light emitting device comprising:
light emitting diode (LED) semiconductor layers comprising an N-type layer, an active layer emitting primary light, and a P-type layer; and
luminescent sapphire affixed to the semiconductor layers, the LED semiconductor layers and the luminescent sapphire being part of an LED die, the luminescent sapphire comprising oxygen vacancies resulting in F-like centers having defined optical absorption and luminescence emission bands;
wherein the luminescent sapphire absorbs a portion of the primary light and down-converts the primary light to emit secondary light, via the F-like centers, such that an emission from the LED die includes at least a combination of the primary light and the secondary light.
2 . The device of claim 1 wherein the luminescent sapphire comprises luminescent sapphire particles combined with a binder to form a mixture, wherein the mixture is located overlying a light emitting surface of the LED semiconductor layers.
3 . The device of claim 2 wherein the mixture is laminated over the semiconductor layers.
4 . The device of claim 2 wherein the mixture is molded over the semiconductor layers.
5 . (canceled)
6 . The device of claim 2 wherein the mixture is located directly on one of the LED semiconductor layers.
7 . The device of claim 1 wherein the luminescent sapphire comprises a pre-formed tile that is affixed over a light emitting surface of the LED semiconductor layers.
8 . The device of claim 7 wherein the tile comprises a single crystal of the luminescent sapphire.
9 . The device of claim 7 wherein the tile comprises luminescent sapphire particles in a binder.
10 . The device of claim 7 wherein the tile is directly affixed to one of the LED semiconductor layers with an adhesive layer.
11 . The device of claim 1 wherein the N-type layer, the active layer, and the P-type layer are epitaxially grown upon a luminescent sapphire growth substrate, wherein the luminescent sapphire comprises the luminescent sapphire growth substrate.
12 . The device of claim 1 further comprising a phosphor layer overlying the LED semiconductor layers as part of the LED die, such that a light emission of the LED die comprises the primary light, the secondary light from the luminescent sapphire, and light from the phosphor layer.
13 . The device of claim 12 wherein the primary light is blue light, the secondary light includes a green light component, and the light from the phosphor layer includes a red light component.
14 . The device of claim 1 wherein the primary light is blue light and the secondary light includes a green light component.
15 . A method comprising:
providing a light emitting diode (LED) die comprising LED semiconductor layers generating primary light, and a luminescent sapphire layer down-converting some of the primary light to secondary light, such that light emitted by the LED die comprises at least a combination of the primary light and the secondary light, the luminescent sapphire comprising oxygen vacancies resulting in F-like centers having defined optical absorption and luminescence emission bands; and
conditioning the luminescent sapphire layer in the LED die using a laser to adjust a characteristic of the secondary light.
16 . The method of claim 15 further comprising activating the luminescent sapphire in the LED die by annealing the luminescent sapphire to increase its luminescent properties after the LED die is formed.
17 - 20 . (canceled)