LED with patterned surface features based on emission field patterns
View Patent ↗The escape surface of a light emitting element includes features that include sloped surfaces that have angles of inclination that are based on the direction of peak light output from the light emitting element. If the light output exhibits a number of lobes at different directions, the sloped surfaces may have a corresponding number of different angles of inclination. To minimize the re-injection of light into adjacent features, adjacent features may be positioned to avoid having surfaces that directly face each other. The features may be shaped or positioned to provide a pseudo-random distribution of inclined surfaces across the escape surface, and multiple roughening processes may be used.
1. A light emitting element, comprising:
a first region of a first dopant type;
a second region of a second dopant type different from the first dopant type;
a light emitting layer sandwiched between the first region and the second region;
an escape surface formed in the first region; and
a mirror formed at a distance from the light emitting layer, the mirror being configured to reflect light from the light emitting layer toward the escape surface, wherein:
each of the first and the second regions comprising one or more layers;
the light emitting layer and the mirror have a relative distance of 0.3 to 1 so that:
the light emitting element is configured to emit a light with an angular emission field pattern relative to a surface of the light emitting layer; and
the angular emission field pattern comprises at least one lobe at a peak emission angle that is between about 20 and 75 degrees relative to the surface of the light emitting layer;
wherein the relative distance is defined as d=η*D/λ, η is the index of refraction of the material between the active layer and the mirror, distance D is a distance between the light emitting layer and the mirror, and λ is the wavelength of the emitted light;
the escape surface defines conic features; and
each conic feature comprises a predominant slope that is substantially orthogonal to the peak emission angle.
2. The light emitting element of claim 1 , wherein the predominant slope is biased from the peak emission angle toward angles of greater emission.
3. The light emitting element of claim 2 , wherein the predominant slope is biased to maximize an amount of light that strikes the predominant slope within its escape zone.
4. The light emitting element of claim 1 , wherein the conic features comprise conic pits or conic structures.
5. The light emitting element of claim 4 , wherein the conic features are arranged in an array with a periodic or pseudo-periodic pattern.
6. The light emitting element of claim 5 , wherein a proportion of the escape surface with the predominant slope is proportional to a proportion of a total power associated with the lobe.