High surface quality GaN wafer and method of fabricating same

Abstract

Al x Ga y In z N, wherein 0≦x≦1, 0≦y≦1, 0≦z≦1, and x+y+z=1, characterized by a root mean square surface roughness of less than 1 nm in a 10×10 μm 2 area. The Al x Ga y In z N may be in the form of a wafer, which is chemically mechanically polished (CMP) using a CMP slurry comprising abrasive particles, such as silica or alumina, and an acid or a base. High quality Al x Ga y In z N wafers can be fabricated by steps including lapping, mechanical polishing, and reducing internal stress of said wafer by thermal annealing or chemical etching for further enhancement of its surface quality. CMP processing may be usefully employed to highlight crystal defects of an Al x Ga y In z N wafer.

1 . A wafer comprising Al x Ga y In z N, wherein 0≦x≦1, 0≦y≦1, 0≦z≦1 and x+y+z=1, said wafer having a Ga-side surface characterized by a root mean square (RMS) surface roughness of less than 1 nm in a 10×10 μm 2  area and having a pit density of about 10 6  to about 10 7  pits/cm 2 .  
   
   
       2 . The wafer according to  claim 1 , wherein pits constituting said pit density are less than 0.4 μm in diameter.  
   
   
       3 . The wafer of  claim 1 , wherein the RMS surface roughness of said wafer is less than 0.7 nm in a 10×10 μm 2  area.  
   
   
       4 . The wafer of  claim 1 , wherein the RMS surface roughness of said wafer is less than 0.5 nm in a 10×10 m 2  area.  
   
   
       5 . The wafer of  claim 1 , wherein the RMS surface roughness of said wafer is at least less than 0.4 nm in a 2×2 μm 2  area.  
   
   
       6 . The wafer of  claim 1 , wherein the RMS surface roughness of said wafer is less than 0.2 nm in a 2×2 μm 2  area.  
   
   
       7 . The wafer of  claim 1 , wherein the RMS surface roughness of said wafer is less than 0.15 nm in a 2×2 m 2  area.  
   
   
       8 . The wafer of  claim 1 , characterized by a step structure when observed with an atomic force microscope.  
   
   
       9 . The wafer of  claim 1 , wherein the crystal defects are visible as small pits with diameters of less than 1 μm.  
   
   
       10 . The wafer of  claim 1 , formed by chemically mechanically polishing (CMP) an Al x Ga y In z N wafer blank, using a silica- or alumina-containing CMP slurry.  
   
   
       11 . An epitaxial Al x Ga y In z N crystal structure, comprising an epitaxial Al x Ga y In z N thin film grown on a wafer comprising Al x Ga y In z N, wherein 0≦x≦1, 0≦y≦1, 0≦z≦1 and x+y+z=1, said wafer having a Ga-side surface characterized by a root mean square (RMS) surface roughness of less than 1 nm in a 10×10 μm area and having a pit density of about 10 6  to about 10 7  pits/cm 2 .  
   
   
       12 . The epitaxial Al x Ga y In z N crystal structure of  claim 11 , comprising a wurtzite crystalline thin film.  
   
   
       13 . The epitaxial Al x Ga y In z N crystal structure of  claim 11 , where the epitaxial Al x′ Ga y′ In z′ N thin film has the same composition as the wafer comprising Al x Ga y In z N.  
   
   
       14 . The epitaxial Al x Ga y In z N crystal structure of  claim 11 , where the epitaxial Al x′ Ga y′ In z′ N thin film has a different composition from the wafer comprising Al x Ga y In z N.  
   
   
       15 . The epitaxial Al x Ga y In z N crystal structure of  claim 11 , where the epitaxial Al x′ Ga y′ In z′ N thin film has a graded composition.  
   
   
       16 . An optoelectronic device comprising at least one epitaxial Al x′ Ga y′ In z′ N crystal structure grown on a wafer comprising Al x Ga y In z N, wherein 0≦x≦1, 0≦y≦1, 0≦z≦1 and x+y+z=1, said wafer having a Ga-side surface characterized by a root mean square (RMS) surface roughness of less than 1 nm in a 10×10 μm 2  area and having a pit density of about 10 6  to about 10 7  pits/cm 2 .  
   
   
       17 . The optoelectronic device of  claim 16 , wherein the optoelectronic device is a light emitting diode.  
   
   
       18 . The optoelectronic device of  claim 16 , wherein the optoelectronic device is a blue light laser diode.  
   
   
       19 . The optoelectronic device of  claim 16 , wherein the optoelectronic device is incorporated into a light emitting diode.  
   
   
       20 . The optoelectronic device of  claim 16 , wherein the optoelectronic device is incorporated into a magneto-optic memory device.  
   
   
       21 . The optoelectronic device of  claim 16 , wherein the optoelectronic device is incorporated into a full color light emitting display.  
   
   
       22 . The optoelectronic device of  claim 16 , wherein the optoelectronic device is incorporated into a DVD device.  
   
   
       23 . A microelectronic device comprising at least one epitaxial Al x′ Ga y′ In z′ N crystal structure grown on a wafer comprising Al x Ga y In z N, wherein 0≦x≦1, 0≦y≦1, 0≦z≦1 and x+y+z=1, said wafer having a Ga-side surface characterized by a root mean square (RMS) surface roughness of less than 1 nm in a 10×10 μm 2  area and having a pit density of about 10 6  to about 10 7  pits/cm 2 .  
   
   
       24 . An epitaxial Al x′ Ga y′ In z′ N crystal boule grown on a wafer comprising Al x Ga y In z N, wherein 0≦x≦1, 0≦y≦1, 0≦z≦1 and x+y+z=1, said wafer having a Ga-side surface characterized by a root mean square (RMS) surface roughness of less than 1 nm in a 10×10 μm 2  area and having a pit density of about 10 6  to about 10 7  pits/cm 2 .  
   
   
       25 . Al x Ga y In z N, wherein 0≦x≦1, 0≦y≦1, 0≦z≦1, and x+y+z=1, having a Ga-side surface characterized by a root mean square (RMS) surface roughness of less than 1 nm in a 10×10 μm 2  area and having a pit density of about 10 6  to about 10 7  pits/cm 2 .  
   
   
       26 . GaN, having a Ga-side surface characterized by a root mean square (RMS) surface roughness of less than 1 nm in a 10×10 μm 2  area and having a pit density of about 10 6  to about 10 7  pits/cm 2 .