Semiconductor light-emitting element

Abstract

In a semiconductor light-emitting element, an underlayer is composed of a high crystallinity AlN layer having a FWHM in X-ray rocking curve of 90 seconds or below, and a first cladding layer is composed of an n-AlGaN layer. A light-emitting layer is composed of a base layer made of i-GaN and plural island-shaped single crystal portions made of i-AlGaInN isolated in the base layer.

1. A semiconductor light-emitting element comprising:
 a sapphire single crystal substrate having a surface nitriding layer on a main surface thereof,  
 an underlayer, formed on the surface nitriding layer on the main surface of the substrate, and being made of a first semi-conducting nitride material including Al element and having a full width at half maximum (FWHM) in X-ray rocking curve of 90 seconds or below,  
 a first conductive layer, formed on the underlayer, made of a second semi-conducting nitride material including at least one element selected from the group consisting of Al, Ga and In,  
 a first cladding layer, formed on the first conductive layer, made of a third semi-conducting nitride material including at least one element selected from the group consisting of Al, Ga and In,  
 a light-emitting layer composed of a base layer, formed on the first cladding layer, made of a fourth semi-conducting nitride material including at least one element selected from the group consisting of Al, Ga and In and plural isolated island-shaped single crystal portions, embedded in the base layer, made of a fifth semi-conducting nitride material including at least one element selected from the group consisting of Al, Ga and In and having an in-plane lattice constant larger than that of the third semi-conducting nitride material,  
 a second cladding layer, formed on the light-emitting layer, made of a sixth semi-conducting nitride material including at least one element selected from the group consisting of Al, Ga and In, and  
 a second conductive layer, formed on the second cladding layer, made of a seventh semi-conducting nitride material including at least one element selected from the group consisting of Al, Ga and In,  
 the bandgap of the third semi-conducting nitride material constituting the first cladding layer,  the bandgap of the fourth semi-conducting nitride material constituting the base layer and the bandgap of the fifth semi-conducting nitride material becoming larger by turns to satisfy the following relationship: the band gap of the fourth semi- conducting nitride material>the bandgap of the fifth semi - conducting nitride material.    
 
     
     
       2. A semiconductor ligth-emitting element as defined in  claim 1 , wherein the Al content of the first semi-conducting nitride material constituting the underlayer is set to 50 atomic percentages or over for the total content of III element. 
     
     
       3. A semiconductor light-emitting element as defined in  claim 2 , wherein the first semi-conducting nitride material constituting the underlayer is AlN. 
     
     
       4. A semiconductor light-emitting element as defined in  claim 1 , wherein the second semi-conducting nitride material constituting the first conductive layer includes at least Al element. 
     
     
       5. A semiconductor ligth-emitting element as defined in  claim 4 , wherein the Al content of the second semi-conducting nitride material constituting the first conductive layer is set to 50 atomic percentages or over for the total content of III element. 
     
     
       6. A semiconductor light-emitting element as defined in  claim 5 , wherein the second semi-conducting nitride material constituting the underlayer is AlN. 
     
     
       7. A semiconductor light-emitting element as defined in  claim 1 , wherein the first semi-conducting nitride material constituting the underlayer is made at 1100° C. or over by a MOCVD method. 
     
     
       8. A semiconductor light-emitting element as defined in  claim 7 , wherein the first semi-conducting nitride material constituting the underlayer is made within 1100-1250° C. by a MOCVD method. 
     
     
       9. A semiconductor light-emitting element as defined in  claim 1 , wherein the substrate is composed of a sapphire single crystal substrate, and the underlayer is formed on the main surface of the substrate via the surface-nitriding layer formed at the main surface by a surface-nitriding treatment. 
     
     
       10. A semiconductor light-emitting element as defined in  claim 1 , wherein the difference in in-plane lattice constant between the third semi-conducting nitride material constituting the first cladding layer and the fifth semi-conducting nitride material constituting the island-shaped single crystal portions is set within 0.4-14% by the ratio for the in-plane lattice constant of the first semi-conducting nitride material. 
     
     
       11. A semiconductor light-emitting element as defined in  claim 1 , wherein the plural island-shaped single crystal portions are dispersed in their sizes, and thus, an any color light is emitted from the light-emitting layer entirely. 
     
     
       12. A semiconductor light-emitting element as defined in  claim 11 , wherein the diameters of the island-shaped single crystal portions are dispersed within 5-30 nm, and thus, a given wavelength light is emitted from each island-shaped single crystal portion and a white light is emitted from the light-emitting layer entirely. 
     
     
       13. A semiconductor light-emitting element as defined in  claim 1 , wherein the plural island-shaped single crystal portions are arranged stepwisely in the base layer, and a given wavelength light is emitted from each island-shaped single crystal portion, and thus, an any color light is emitted from the light-emitting layer entirely. 
     
     
       14. A semiconductor light-emitting element as defined in  claim 13 , wherein the sizes of the island-shaped single crystal portions are dispersed in their respective arranged steps in the base layer constituting the light-emitting layer. 
     
     
       15. A semiconductor light-emitting element as defined in  claim 13 , wherein the average sizes of the island-shaped single crystal portions are dispersed over the steps in the base layer constituting the light-emitting layer, and thus, an any color light is emitted from the light-emitting layer entirely. 
     
     
       16. A semiconductor light-emitting element as defined in  claim 15 , wherein the average sizes of the island-shaped single crystal portions are dispersed within 5-30 nm over the steps in the base layer constituting the light-emitting layer, and thus, a given wavelength light is emitted from each island-shaped single crystal portion arranged stepwisely, and a white light is emitted from the light-emitting layer entirely. 
     
     
       17. A semiconductor light-emitting element as defined in  claim 1 , wherein the Al content of the first semi-conducting nitride material constituting the underlayer is continuously or stepwisely decreased to the first conductive layer from the substrate. 
     
     
       18. A semiconductor light- emitting element as defined in    claim 1   , wherein the bandgap of the third semi - conducting nitride material>the bandgap of the fourth semi - conducting nitride material.   
     
     
       19. A semiconductor light- emitting element comprising:      a substrate,        an underlayer having a thickness in a range of  1   -   3  μm formed on a main surface of the substrate, and being made of a first semi - conducting nitride material including Al element and having a full width at half maximum  ( FWHM )  in X - ray rocking curve of  90  seconds or below,        a first conductive layer, formed on the underlayer, made of a second semi - conducting nitride material including at least one element selected from the group consisting of Al, Ga and In,        a first cladding layer, formed on the first conductive layer, made of a third semi - conducting nitride material including at least one element selected from the group consisting of Al, Ga and In,        a light - emitting layer composed of a base layer, formed on the first cladding layer, made of a fourth semi - conducting nitride material including at least one element selected from the group consisting of Al, Ga and In and plural isolated island - shaped single crystal portions, embedded in the base layer, made of a fifth semi - conducting nitride material including at least one element selected from the group consisting of Al, Ga and In and having an in - plane lattice constant larger than that of the third semi - conducting nitride material,        a second cladding layer, formed on the light - emitting layer, made of a sixth semi - conducting nitride material including at least one element selected from the group consisting of Al, Ga and In, and        a second conductive layer, formed on the second cladding layer, made of a seventh semi - conducting nitride material including at least one element selected from the group consisting of Al, Ga and In,        the bandgap of the fourth semi - conducting nitride material constituting the base layer and the bandgap of the fifth semi - conducting nitride material becoming larger by turns to satisfy the following relationship: the bandgap of the fourth semi - conducting nitride material>the bandgap of the fifth semi - conducting nitride material.