Low optical loss electrode structures for LEDs
View Patent ↗An electrode structure is disclosed for enhancing the brightness and/or efficiency of an LED. The electrode structure can have a metal electrode and an optically transmissive thick dielectric material formed intermediate the electrode and a light emitting semiconductor material. The electrode and the thick dielectric cooperate to reflect light from the semiconductor material back into the semiconductor so as to enhance the likelihood of the light ultimately being transmitted from the semiconductor material. Such LED can have enhanced utility and can be suitable for uses such as general illumination.
1. A reflective electrode structure comprising:
an electrode;
a semiconductor material configured to emit light about a central wavelength λ;
a dielectric material formed upon the semiconductor material;
at least one DBR pair formed upon the dielectric material; and
wherein a portion of the electrode is formed over both the dielectric material and the DBR pair(s) and another portion of the electrode is in ohmic contact with the semiconductor material.
2. The reflective electrode structure as recited in claim 1 , wherein the electrode comprises a metal electrode.
3. The reflective electrode structure as recited in claim 1 , wherein the semiconductor material comprises GaN.
4. The reflective electrode structure as recited in claim 1 , wherein the dielectric material comprises at least one material selected from the group consisting of:
silicon dioxide;
silicon monoxide;
MgF 2 ; and
siloxane polymers.
5. The reflective electrode structure as recited in claim 1 , wherein the dielectric material comprises silicon dioxide.
6. The reflective electrode structure as recited in claim 1 , wherein the dielectric material has a thickness of approximately 1.75λ.
7. A reflective electrode structure comprising:
a metal electrode;
a GaN semiconductor material configured to emit light about a central wavelength λ;
silicon dioxide dielectric material formed upon the GaN material, the dielectric material having a thickness of approximately 1.75λ;
at least one DBR pair formed upon the silicon dioxide material; and
wherein a portion of the electrode is formed over both the dielectric material and the DBR pair(s) and another portion of the electrode is in ohmic contact with the semiconductor material.
8. The reflective electrode structure as recited in claim 7 , wherein each layer of the DBR pair(s) is optically transmissive and has a different index of refraction with respect to each other layer.
9. The reflective electrode structure as recited in claim 7 , wherein each layer of the DBR pair(s) has a thickness that is a multiple of approximately ¼λ.
10. The reflective electrode structure as recited in claim 7 , wherein the dielectric and the electrode make physical contact to the semiconductor via an ITO layer.