Enhancement of optical polarization of nitride light-emitting diodes by increased indium incorporation

Abstract

An increase in the Indium (In) content in light-emitting layers of light-emitting diode (LED) structures prepared on nonpolar III-nitride substrates result in higher polarization ratios for light emission than LED structures containing lesser In content. Polarization ratios should be higher than 0.7 at wavelengths longer than 470 nm.

What is claimed is: 
     
         1 . A light-emitting diode (LED) that emits polarized light, comprising:
 one or more III-nitride light-emitting layers formed on one or more III-nitride layers, wherein the III-nitride light-emitting layers have an Indium (In) content that results in a higher polarization ratio of light emitted by the III-nitride light-emitting layers as compared to III-nitride light-emitting layers containing a lesser Indium (In) content.   
     
     
         2 . The LED of  claim 1 , wherein the Indium (In) content is such that the polarization ratio of the polarized light emitted by the III-nitride light-emitting layers is greater than 0.8. 
     
     
         3 . The LED of  claim 2 , wherein the Indium (In) content increases a strain in the III-nitride light-emitting layers due to an increased lattice mismatch, in order to increase the polarization ratio above 0.8. 
     
     
         4 . The LED of  claim 1 , wherein the III-nitride light-emitting layers are prepared epitaxially on a nonpolar orientation of a wurtzite crystal. 
     
     
         5 . The LED of  claim 4 , wherein the III-nitride light-emitting layers are prepared epitaxially on a GaN substrate or GaN template. 
     
     
         6 . The LED of  claim 5 , wherein the GaN template is a GaN layer prepared on a foreign substrate. 
     
     
         7 . The LED of  claim 4 , wherein the III-nitride light-emitting layers are prepared on a III-nitride substrate or template that is not GaN. 
     
     
         8 . The LED of  claim 1 , wherein the III-nitride light-emitting layers comprise a quantum-well (QW) structure or double-hetero (DH) structure, and the QW or DH structure includes a light-emitting active layer embedded between one or more barrier layers or cladding layers that have a larger band gap than a band gap of the active layer. 
     
     
         9 . The LED of  claim 8 , wherein the active layer is embedded between one or more In y GaN or GaN layers that have smaller Indium (In) content (y) value than a y value of the active layer. 
     
     
         10 . The LED of  claim 8 , wherein the active layer comprises In y GaN with an Indium (In) content y in a range 0<y≦1, the Indium (In) content controls induced strain in the active layer, and the induced strain controls a degree of polarization of the polarized light. 
     
     
         11 . The LED of  claim 8 , wherein the active layer is AlInGaN to adjust strain. 
     
     
         12 . A method of fabricating a light-emitting diode (LED), comprising:
 forming one or more III-nitride light-emitting layers on one or more III-nitride layers, wherein the III-nitride light-emitting layers have an Indium (In) content that results in a higher polarization ratio of light emitted by the III-nitride light-emitting layers as compared to III-nitride light-emitting layers containing a lesser Indium (In) content.   
     
     
         13 . The method of  claim 12 , wherein the Indium (In) content is such that the polarization ratio of the polarized light emitted by the III-nitride light-emitting layers is greater than 0.8. 
     
     
         14 . The method of  claim 13 , wherein the Indium (In) content increases a strain in the III-nitride light-emitting layers due to an increased lattice mismatch, in order to increase the polarization ratio above 0.8. 
     
     
         15 . The method of  claim 12 , wherein the III-nitride light-emitting layers are prepared epitaxially on a nonpolar orientation of a wurtzite crystal. 
     
     
         16 . The method of  claim 15 , wherein the III-nitride light-emitting layers are prepared epitaxially on a GaN substrate or GaN template. 
     
     
         17 . The method of  claim 16 , wherein the GaN template is a GaN layer prepared on a foreign substrate. 
     
     
         18 . The method of  claim 15 , wherein the III-nitride light-emitting layers are prepared on a III-nitride substrate or template that is not GaN. 
     
     
         19 . The method of  claim 12 , wherein the III-nitride light-emitting layers comprise a quantum-well (QW) structure or double-hetero (DH) structure, and the QW or DH structure includes a light-emitting active layer embedded between one or more barrier layers or cladding layers that have a larger band gap than a band gap of the active layer. 
     
     
         20 . The method of  claim 19 , wherein the active layer is embedded between one or more In y GaN or GaN layers that have smaller Indium (In) content (y) value than a y value of the active layer. 
     
     
         21 . The method of  claim 19 , wherein the active layer comprises In y GaN with an Indium (In) content y in a range 0<y≦1, the Indium (In) content controls induced strain in the active layer, and the induced strain controls a degree of polarization of the polarized light. 
     
     
         22 . The method of  claim 19 , wherein the active layer is AlInGaN to adjust strain.