Nanostructured led array with collimating reflectors

Abstract

The present invention relates to nanostructured light emitting diodes, LEDs. The nanostructured LED device according to the invention comprises an array of a plurality of individual nanostructured LEDs. Each of the nanostructured LEDs has an active region wherein light is produced. The nanostructured device further comprise a plurality of reflectors, each associated to one individual nanostructured LED (or a group of nanostructured LEDs. The individual reflectors has a concave surface facing the active region of the respective individual nanostructured LED or active regions of group of nanostructured LEDs.

1 . A nanostructured LED device ( 101 ) comprising an array comprising a plurality of individual nanostructured LEDs ( 100 ), each nanostructured LED ( 100 ) of said plurality of LEDs comprising an active region ( 120 ) for light emission, and a plurality of reflectors ( 135 ), each associated to an individual nanostructured LED ( 100 ) of said plurality of LEDs or a group of nanostructured LEDs ( 100 ) of said plurality of LEDs, and each reflector ( 135 ) of said plurality of reflectors having a concave surface facing an active region of the respective individual nanostructured LED or active regions of the respective group of nanostructured LEDs. 
     
     
         2 . The nanostructured LED device ( 101 ) according to  claim 1 , wherein each reflector ( 135 ) of said plurality of reflectors is positioned over a centre of the respective individual nanostructured LED ( 100 ) as seen from a top of the nanostructured LEDs. 
     
     
         3 . The nanostructured LED device ( 101 ) according to  claim 1 , wherein each reflector ( 135 ) of said plurality of reflectors covers a combined upper surfaces of the respective group of nanostructured LEDs. 
     
     
         4 . The nanostructured LED device ( 101 ) according to  claim 2 , wherein each reflector ( 135 ) of said plurality of reflectors covers an upper surface of the respective nanostructured LED ( 100 ). 
     
     
         5 . The nanostructured LED device ( 101 ) according to  claim 4 , wherein the concave surface of each reflector ( 135 ) of said plurality of reflectors is defined by a shape of the upper surface of the respective nanostructured LED ( 100 ). 
     
     
         6 . The nanostructured LED device ( 101 ) according to  claim 5 , wherein the plurality of nanostructured LEDs ( 100 ) comprise a plurality of elongated structures, each having a pointed upper part and a vertical side surface, wherein the respective reflector ( 135 ) of said plurality of reflectors covers at least the pointed upper part of the respective elongated structure. 
     
     
         7 . The nanostructured LED device ( 101 ) according to  claim 6 , wherein the respective reflector ( 135 ) of said plurality of reflectors covers a portion of the vertical side surface of the respective elongated structure. 
     
     
         8 . The nanostructured LED device ( 101 ) according to  claim 5 , wherein the plurality of nanostructured LEDs ( 100 ) comprise a plurality of pyramidal structures. 
     
     
         9 . The nanostructured LED device ( 101 ) according to  claim 1 , wherein the reflectors ( 135 ) also are an upper contact to the respective nanostructured LED or the respective group of nanostructured LEDs. 
     
     
         10 . The nanostructured LED device ( 101 ) according to  claim 1 , wherein the array forms a photonic crystal that is arranged to inhibit a wavelength of the light emitted from the active regions of the plurality of nanostructured LEDs in a direction close to a plane of the array. 
     
     
         11 . The nanostructured LED device ( 101 ) according to  claim 1 , wherein the plurality of reflectors ( 135 ) are joined to form a continuous reflecting layer ( 535 ) covering the plurality of nanostructured LEDs ( 100 ). 
     
     
         12 . The nanostructured LED device ( 101 ) according to  claim 11 , further comprising a fill layer ( 507 ) that covers a portion of the plurality of nanostructured LEDs, and wherein the continuous reflecting layer ( 535 ) covers at least an upper surface of the plurality of nanostructured LEDs and the fill layer in between nanostructured LEDs of said plurality of LEDs. 
     
     
         13 . The nanostructured LED device ( 101 ) according to  claim 1 , wherein the plurality of nanostructured LEDs ( 100 ) comprise waveguides adapted to direct at least a portion of emitted light towards a respective reflector ( 135 ) of the plurality of reflectors. 
     
     
         14 . The nanostructured LED device ( 101 ) according to  claim 1 , wherein the plurality of nanostructured LEDs forms a LED array layer, with a corresponding plurality of active regions ( 120 ) arranged in the LED array layer, and a reflector layer ( 181 ) arranged in a plane parallel to the LED array layer ( 180 ), the reflector layer comprising a plurality of reflectors ( 135 ) each having a concave surface facing one or a group of the active regions ( 120 ) and arranged to direct light through the LED array ( 180 ). 
     
     
         15 . The nanostructured LED device ( 101 ) according to  claim 14 , wherein individual nanostructured LEDs in the LED array layer ( 180 ) and individual reflectors in the reflector layer ( 181 ) are periodically repeated and a periodicity of the individual reflectors ( 135 ) of the reflector layer ( 181 ) is related to a periodicity of the individual nanostructured LEDs in the LED array layer ( 180 ). 
     
     
         16 . The nanostructured LED device ( 101 ) according to  claim 14 , wherein each reflector ( 135 ) of the reflector layer ( 181 ) is positioned over a centre of the respective nanostructured LED ( 100 ) of the LED array layer ( 180 ) as seen from a top of the nanostructured LEDs. 
     
     
         17 . The nanostructured LED device ( 101 ) according to  claim 15 , wherein the periodicity of the reflectors ( 135 ) of the reflector layer ( 181 ) is related to the periodicity of the individual nanostructured LEDs in the LED array layer ( 180 ) as a series of n or 1/n, wherein n is an integer. 
     
     
         18 . The nanostructured LED device ( 101 ) according to  claim 14 , wherein individual nanostructured LEDs in the LED array layer ( 180 ) and individual reflectors in the reflector layer ( 181 ) are periodically repeated and a periodicity of the individual reflectors ( 135 ) of the reflector layer ( 181 ) is uncorrelated to a periodicity of the individual nanostructured LEDs in the LED array layer ( 180 ). 
     
     
         19 . The nanostructured LED device ( 101 ) according to  claim 14 , wherein each reflector ( 135 ) of the reflector layer ( 181 ) covers an upper surface of the respective nanostructured LED ( 100 ) of the LED array layer ( 180 ). 
     
     
         20 . The nanostructured LED device ( 101 ) according to  claim 14 , wherein individual reflectors ( 135 ) of the plurality of reflectors are joined to form a continuous reflecting layer ( 535 ) covering the plurality of nanostructured LEDs ( 100 ). 
     
     
         21 . The nanostructured LED device ( 101 ) according to  claim 20 , further comprising a fill layer ( 507 ) that covers a portion of the plurality of nanostructured LEDs, and wherein the continuous reflecting layer ( 535 ) covers at least an upper surface of the plurality of nanostructured LEDs and the fill layer in between nanostructured LEDs of said plurality of LEDs. 
     
     
         22 . The nanostructured LED device ( 101 ) according to  claim 14 , wherein the array forms a photonic crystal in the LED array layer ( 180 ), the photonic crystal arranged to inhibit a wavelength of the light emitted from the active regions of the LED array layer ( 180 ) in a direction close to a plane of the array. 
     
     
         23 . A method of fabricating a nanostructured LED device comprising a plurality of nanostructured LEDs, comprising the steps of:
 (a) defining growth positions on a substrate by lithography;   (b) growing nanostructured LEDs from the substrate on the defined growth positions; and   (c) depositing a reflector material at least on top of the grown nanostructured LEDs, thereby forming individual reflectors for each of the nanostructured LEDs.   
     
     
         24 . The method of fabricating a nanostructured LED according to  claim 23 , further comprising a step, to be taken after the step of growing of nanostructured LEDs and prior to the step of depositing a reflector material, of forming upper parts of the nanostructured LEDs to define a shape of an inner surface of the reflectors covering the nanostructured LEDs. 
     
     
         25 . The method of fabricating a nanostructured LED according to  claim 24 , wherein the step of forming the upper parts of the nanostructured LEDs comprises removing a material from the upper parts of the nanostructured LEDs to provide the nanostructured LEDs with a predetermined shape. 
     
     
         26 . The method of fabricating a nanostructured LED according to  claim 24 , wherein the step of forming the upper parts of the nanostructured LEDs comprises adding a transparent material at least on top of the nanostructured LEDs to form a predetermined shape to define the inner surface of the reflectors. 
     
     
         27 . The nanostructured LED device according to  claim 8 , wherein for an individual pyramidal structure of said plurality of pyramidal structures, an active region of a nanostructured LED is formed on the pyramidal structure, said active region comprises a p-n junction. 
     
     
         28 . The nanostructured LED device ( 101 ) according to  claim 1 , wherein the plurality of nanostructured LEDs forms a LED array layer, with a corresponding plurality of active regions ( 120 ) arranged in the LED array layer, and a reflector layer ( 181 ) arranged in a plane parallel to the LED array layer ( 180 ), wherein individual reflectors of the reflector layer having a random configuration or a periodicity which is not correlated to a periodicity of individual nanostructured LEDs of the LED array layer.