High-efficiency micro-LEDs
Disclosed herein are light emitting diodes (LEDs) having a high efficiency. A light emitting diode including an active light emitting layer within a semiconductor layer is provided. The semiconductor layer has a mesa shape. The light emitting diode also includes a substrate having a first surface on which the semiconductor layer is positioned and an outcoupling surface opposite to the first surface. Light generated by the active light emitting layer is incident on the outcoupling surface and propagates toward an optical element downstream of the outcoupling surface. The light emitting diode also includes a first anti-reflection coating adjacent to the outcoupling surface; an index-matched material between the outcoupling surface and the optical element, wherein an index of refraction of the index-matched material is greater than or equal to an index of refraction of the optical element; and/or secondary optics adjacent to the outcoupling surface.
1. A light emitting diode comprising:
an active light emitting layer within a semiconductor layer, wherein the semiconductor layer has a mesa shape;
a substrate comprising a first surface on which the semiconductor layer is positioned and an outcoupling surface opposite to the first surface, wherein light generated by the active light emitting layer is incident on the outcoupling surface and propagates toward an optical element downstream of the outcoupling surface; and
secondary optics adjacent to the outcoupling surface, wherein:
the semiconductor layer comprises an n-side semiconductor layer adjacent to the substrate and a p-side semiconductor layer opposite to the active light emitting layer,
the secondary optics comprise a lens having a focal point at the active light emitting layer, and
a diameter of the lens is greater than a diameter of the outcoupling surface of the substrate.
2. The light emitting diode of claim 1 , wherein the mesa shape is substantially vertical.
3. The light emitting diode of claim 1 , wherein the mesa shape is substantially non-vertical.
4. The light emitting diode of claim 1 , wherein the mesa shape is at least one of conical, semi-parabolic, or parabolic.
5. The light emitting diode of claim 1 , wherein a base area of the mesa shape is at least one of circular, rectangular, hexagonal, or triangular.
6. The light emitting diode of claim 1 , wherein the lens is made of a first material, and the semiconductor layer is made of a second material that is different from the first material.
7. The light emitting diode of claim 1 , wherein the lens is a spherical lens.
8. The light emitting diode of claim 1 , wherein the lens is sized such that the light emitting diode has a light extraction efficiency between 2% and 6% within an emission cone having an angle of 10°.
9. A light emitting diode comprising:
an active light emitting layer within a semiconductor layer, wherein the semiconductor layer has a mesa shape;
a substrate comprising a first surface on which the semiconductor layer is positioned and an outcoupling surface opposite to the first surface, wherein light generated by the active light emitting layer is incident on the outcoupling surface and propagates toward an optical element downstream of the outcoupling surface; and at least one of:
a first anti-reflection coating adjacent to the outcoupling surface;
an index-matched material between the outcoupling surface and the optical element, wherein an index of refraction of the index-matched material is greater than or equal to an index of refraction of the optical element; or
secondary optics adjacent to the outcoupling surface, wherein:
the semiconductor layer comprises an n-side semiconductor layer adjacent to the substrate and a p-side semiconductor layer opposite to the active light emitting layer,
the mesa shape is non-planar,
the mesa shape is symmetric about an axis perpendicular to the outcoupling surface,
light exiting the outcoupling surface has a first beam profile that is non-planar due to the mesa shape being non-planar, and
the secondary optics is configured to collimate the light exiting the outcoupling surface such that light emitted by the secondary optics has a second beam profile that is narrower than the first beam profile and has a half width at half-maximum (HWHM) less than or equal to 60°.