High efficiency light emitting diode (led) with optimized photonic crystal extractor

Abstract

A high efficiency, and possibly highly directional, light emitting diode (LED) with an optimized photonic crystal extractor. The LED is comprised of a substrate, a buffer layer grown on the substrate (if needed), an active layer including emitting species, one or more optical confinement layers that tailor the structure of the guided modes in the LED, and one or more diffraction gratings, wherein the diffraction gratings are two-dimensional photonic crystal extractors. The substrate may be removed and metal layers may be deposited on the buffer layer, photonic crystal and active layer, wherein the metal layers may function as a mirror, an electrical contact, and/or an efficient diffraction grating.

1 . A light emitting diode (LED), comprising:
 (a) one or more active layers for generating light;   (b) one or more photonic crystals for extracting the light out of the LED; and   (c) one or more light confining layers for exciting one or more modes of the light for extraction by the photonic crystals.   
     
     
         2 . The LED of  claim 1 , wherein the light confining layers are formed under or around the active layers. 
     
     
         3 . The LED of  claim 1 , wherein the light confining layers excite modes localized above the light confining layers for extraction by the photonic crystals. 
     
     
         4 . The LED of  claim 1 , wherein the photonic crystals are diffraction gratings. 
     
     
         5 . The LED of  claim 1 , wherein the photonic crystals pierce the active layers. 
     
     
         6 . The LED of  claim 1 , wherein the photonic crystals are situated within one or a few optical lengths of the active layers. 
     
     
         7 . The LED of  claim 1 , wherein the active layers coincide or overlap with the photonic crystals, so that guided modes of the light do not reflect or scatter at an interface between the active layers and the photonic crystals. 
     
     
         8 . The LED of  claim 1 , wherein the photonic crystals include one or more tapers comprised of variable hole lines. 
     
     
         9 . The LED of  claim 8 , wherein the tapers comprise one or more periods of modified holes, and the modified holes have a variable hole depth, variable hole period, or variable hole diameter. 
     
     
         10 . The LED of  claim 1 , wherein characteristics of the photonic crystals are varied along its structure, so as to modify light extraction properties of the photonic crystals. 
     
     
         11 . The LED of  claim 1 , wherein the LED is a planar structure. 
     
     
         12 . A method for fabricating a light emitting diode (LED), comprising:
 (a) forming one or more active layers for generating light;   (b) forming one or more photonic crystals for extracting the light out of the LED; and   (c) forming one or more light confining layers for exciting one or more modes of the light for extraction by the photonic crystals.   
     
     
         13 . The method of  claim 12 , wherein the light confining layers are formed under or around the active layers. 
     
     
         14 . The method of  claim 12 , wherein the light confining layers excite modes localized above the light confining layers for extraction by the photonic crystals. 
     
     
         15 . The method of  claim 12 , wherein the photonic crystals are diffraction gratings. 
     
     
         16 . The method of  claim 12 , wherein the photonic crystals pierce the active layers. 
     
     
         17 . The method of  claim 12 , wherein the photonic crystals are situated within one or a few optical lengths of the active layers. 
     
     
         18 . The method of  claim 12 , wherein the active layers coincide or overlap with the photonic crystals, so that guided modes of the light do not reflect or scatter at an interface between the active layers and the photonic crystals. 
     
     
         19 . The method of  claim 12 , wherein the photonic crystals include one or more tapers comprised of variable hole lines. 
     
     
         20 . The method of  claim 19 , wherein the tapers comprise one or more periods of modified holes, and the modified holes have a variable hole depth, variable hole period, or variable hole diameter. 
     
     
         21 . The method of  claim 12 , wherein characteristics of the photonic crystals are varied along its structure, so as to modify light extraction properties of the photonic crystals. 
     
     
         22 . The method of  claim 12 , wherein the LED is a planar structure.