Surface textured LEDs and method for making the same
View Patent ↗A light-emitting device that includes an LED and a light extraction layer and the method for making the same are disclosed. The LED includes a substrate on which an active layer is sandwiched between a p-type layer and an n-type layer, the active layer generating light in a band of wavelengths about a central wavelength when holes and electrons recombine therein. The n-type layer, active layer, and p-type layer are formed on the substrate. First and second electrodes for providing a potential difference between the p-type layer and the n-type layer are included in the LED. The light extraction layer includes a clear layer of material having a first surface in contact with a surface of the LED and a second surface having light scattering features with dimensions greater than 0.5 times the central wavelength. The material of the clear layer can be polycrystalline or amorphous.
1. A light-emitting device comprising an LED and a light extraction layer, the LED comprising:
a substrate having a first surface and an opposing second surface;
an active layer sandwiched between a first layer having a first type of doping and a second layer having a second type of doping, the active layer generating light when holes and electrons recombine therein, the first layer, active layer, and second layer located on the first surface of the substrate, the first and second layers being substantially planar;
a first electrode connected to the first layer, the first electrode being substantially transparent, and substantially planar;
a second electrode connected to the second layer; the first electrode and the second electrode configured to provide a potential difference between the first layer and the second layer; and
the light extraction layer located on the second surface of the substrate, the light extraction layer comprising:
a clear layer of material with a top surface and a bottom surface; and
random light scattering features located on the bottom surface of the clear layer of material;
wherein the top surface of the clear layer of material is substantially planar and connected to the second surface of the substrate and wherein the index of refraction of the light extraction layer is equal to or greater than that of the substrate, and less than or equal to that of the surrounding medium of the substrate, wherein light entering the surrounding medium from the light extraction layer not under a condition of total internal reflection exits the light extraction layer through the surrounding medium.
2. The light-emitting device of claim 1 , wherein the clear layer of material is an amorphous material chosen from the group consisting of glass and polymers.
3. The light-emitting device of claim 1 , wherein the clear layer of material has an index of refraction greater than 2.
4. The light-emitting device of claim 1 , wherein the substrate comprises sapphire or SiC.
5. The light-emitting device of claim 1 , wherein the light extraction layer is on a first side of the light-emitting device and the first and second electrodes are on an opposing second side of the light-emitting device.
6. The light-emitting device of claim 1 , wherein the light extraction layer is formed from moldable plastics or moldable polymers.
7. The light-emitting device of claim 1 , wherein the light extraction layer has a thickness at least 3 wavelengths of light thick.
8. The light-emitting device of claim 1 , wherein light emitted from the light-emitting device is in a band of wavelengths about a central wavelength and wherein the random light scattering features have dimensions greater than 0.5 times the central wavelength.