Narrowband reflector for micro-LED arrays
A structure and method of micro-LEDs are described. The micro-LEDs have a GaN semiconductor structure containing a multi-quantum well active region configured to emit light of a visible wavelength range and a multilayer reflector structure that includes a distributed Bragg reflector (DBR) with a maximum reflectance at the visible wavelength range and to reflect the light emitted by the active region towards an emission surface of the semiconductor structure. The multilayer reflector structure also has a protective layer between the DBR and the GaN structure that is transparent to light of visible wavelengths. The multilayer reflector structure also has an absorbing metal layer that absorbs the light of visible wavelengths. A conductive material provides electrically contact to the semiconductor structure.
1 . A micro-light-emitting diode (LED) comprising:
a semiconductor structure containing an active region configured to emit light of a predetermined visible wavelength range;
a multilayer reflector structure disposed on a surface of the semiconductor structure opposing an emission surface of the semiconductor structure, the multilayer reflector structure including a narrowband reflector configured to have a maximum reflectance at the predetermined visible wavelength range and to reflect the light emitted by the active region towards the emission surface of the semiconductor structure;
a protective layer disposed between the narrowband reflector and the semiconductor structure, the protective layer substantially transparent to light of visible wavelengths;
a transparent conductive film disposed between the protective layer and the semiconductor structure, the transparent conductive film disposed on the semiconductor structure; and
an anti-reflecting coating disposed at an interface between transparent conductive film and the protective layer.
2 . The micro-LED of claim 1 , wherein the protective layer comprises silicon dioxide.
3 . The micro-LED of claim 1 , wherein the multilayer reflector structure further comprises an absorbing layer configured to absorb the light of visible wavelengths, the narrowband reflector disposed between the absorbing layer and the semiconductor structure.
4 . The micro-LED of claim 3 , wherein the absorbing layer comprises TiW.
5 . The micro-LED of claim 1 , further comprising:
an encapsulant that encapsulates the semiconductor structure and the multilayer reflector structure, the encapsulant transparent to visible light.
6 . The micro-LED of claim 1 , wherein the narrowband reflector comprises a distributed Bragg reflector (DBR).
7 . The micro-LED of claim 1 , further comprising an eVia comprising a conductive material configured to electrically contact the semiconductor structure, the multilayer reflector structure laterally surrounding the e Via.
8 . The micro-LED of claim 7 , wherein:
the conductive material comprises Cu plated with AgTiW to contact a p doped region of the semiconductor structure, and
a Cu layer with thin layer of Al contacts sidewalls of an n doped region of the semiconductor structure.
9 . The micro-LED of claim 1 , wherein the active region comprises a multi-quantum well structure.
10 . A micro-light-emitting diode (LED) system comprising:
a plurality of micro-LEDs configured to emit light of different wavelength ranges, each micro-LED comprising:
a semiconductor structure containing an active region configured to emit light of a predetermined visible wavelength range;
a multilayer reflector structure that includes a distributed Bragg reflector (DBR) configured to have a maximum reflectance at the predetermined visible wavelength range and to reflect the light emitted by the active region towards an emission surface of the semiconductor structure;
a protective layer disposed between the DBR and the semiconductor structure, the protective layer substantially transparent to light of visible wavelengths;
a transparent conductive film disposed between the protective layer and the semiconductor structure, the transparent conductive film disposed on the semiconductor structure; and
an anti-reflecting coating disposed at an interface between transparent conductive film and the protective layer; and
control circuitry configured to individually drive each of the micro-LEDs.
11 . The micro-LED system of claim 10 , wherein:
the multilayer reflector structure is disposed on a surface of the semiconductor structure opposing the emission surface, and
the multilayer reflector structure further comprises:
an absorbing layer configured to absorb the light of visible wavelengths, the DBR disposed between the absorbing layer and the semiconductor structure.
12 . The micro-LED system of claim 10 , wherein:
each micro-LED further comprises an eVia comprising a conductive material configured to electrically contact the semiconductor structure, the multilayer reflector structure of the micro-LED laterally surrounds the e Via, and
the control circuitry is configured to control activation of the micro-LED through the eVia.
13 . A micro-light-emitting diode (LED) comprising:
a semiconductor structure containing an active region configured to emit light of a predetermined visible wavelength range;
a multilayer reflector structure that includes a narrowband reflector configured to have a maximum reflectance at the predetermined visible wavelength range and to reflect the light emitted by the active region towards an emission surface of the semiconductor structure; and
an eVia comprising a conductive material configured to electrically contact the semiconductor structure, the multilayer reflector structure laterally surrounding the eVia,
wherein the conductive material comprises Cu plated with AgTiW to contact a p doped region of the semiconductor structure, and a Cu layer with thin layer of Al contacts sidewalls of an n doped region of the semiconductor structure.
14 . The micro-LED of claim 13 , wherein the multilayer reflector structure is disposed on a surface of the semiconductor structure opposing the emission surface.
15 . The micro-LED of claim 14 , wherein the multilayer reflector structure further comprises a protective layer disposed between the narrowband reflector and the semiconductor structure, the protective layer substantially transparent to light of visible wavelengths.
16 . The micro-LED of claim 15 , wherein the protective layer comprises silicon dioxide.
17 . The micro-LED of claim 13 , wherein the multilayer reflector structure further comprises an absorbing layer configured to absorb the light of visible wavelengths, the narrowband reflector disposed between the absorbing layer and the semiconductor structure.
18 . The micro-LED of claim 15 , further comprising a transparent conductive film disposed between the protective layer and the semiconductor structure, the transparent conductive film disposed on the semiconductor structure.
19 . The micro-LED of claim 13 , further comprising:
an encapsulant that encapsulates the semiconductor structure and the multilayer reflector structure, the encapsulant transparent to visible light; and
an anti-reflecting coating disposed at an interface between the encapsulant and air.
20 . The micro-LED of claim 13 , further comprising:
an encapsulant that encapsulates the semiconductor structure and the multilayer reflector structure, the encapsulant transparent to visible light; and
an anti-reflecting coating disposed at an interface between the encapsulant and the semiconductor structure.