Light emitting diode with low refractive index material layers to reduce light guiding effects

Abstract

A light-emitting diode (LED) for emitting emitted light having a particular wavelength, said LED comprising: (a) at least one n-doped layer; (b) at least one p-doped layer; (c) an active region comprising at least one layer of light-emitting material disposed between said at least one n-doped layer and said at least one p-doped layer, said active region having an average refractive index, calculated by averaging the LED's refractive index across the thickness of the active region; and (d) at least one low refractive index layer disposed within said particular wavelength of said active region, said at least one low refractive index layer having a refractive index below said average refractive index and a thickness sufficient to limit light being emitted into a guided mode of said active region to no more than 10% of said emitted light.

What is claimed is: 
     
         1 . (canceled) 
     
     
         2 . A device comprising:
 a substrate;   a low-index layer comprising at least one AlInN layer overlying the substrate;   an intermediate layer having a thickness, overlying the low-index layer;   an active region overlying the intermediate layer, configured to emit light characterized by an optical wavelength;   wherein the thickness is such that a distance between the active region and the low-index layer is less than the optical wavelength; and   wherein the index of the at least one AlInN layer at the optical wavelength is at least 0.05 less than the index of GaN at the optical wavelength.   
     
     
         3 . The device of  claim 2 , wherein the at least one AlInN layer is lattice-matched to GaN. 
     
     
         4 . The device of  claim 2 , wherein the low-index layer is n-doped. 
     
     
         5 . The device of  claim 2 , wherein the low-index layer has a homogeneous composition. 
     
     
         6 . The device of  claim 2 , wherein the low-index layer has a graded composition. 
     
     
         7 . The device of  claim 2 , wherein the low-index layer comprises a succession of AlInN layers and other layers. 
     
     
         8 . The device of  claim 7 , wherein the succession forms a superlattice. 
     
     
         9 . The device of  claim 7 , wherein the other layers comprise at least one of GaN, AlGaN or InGaN. 
     
     
         10 . The device of  claim 2 , wherein the active region comprises at least one quantum well. 
     
     
         11 . The device of  claim 10 , wherein the active region comprises multiple quantum wells. 
     
     
         12 . The device of  claim 2 , wherein the substrate comprises GaN. 
     
     
         13 . The device of  claim 12 , wherein the substrate is a bulk GaN substrate. 
     
     
         14 . The device of  claim 2 , further comprising an electron blocking layer overlying the active region 
     
     
         15 . The light-emitting diode of  claim 2 , wherein less than 10% of total light emitted by the active region is guided by the active region. 
     
     
         16 . The light-emitting diode of  claim 2 , wherein the optical wavelength is within a range from about 200 nm to about 1000 nm. 
     
     
         17 . The light-emitting diode of  claim 16 , wherein the low-index layer is within 500 nm of the active region. 
     
     
         18 . The light-emitting diode of  claim 2 , wherein the at least one AlInN layer has a thickness of about 40 nm