Method and apparatus for fabricating crack-free group iii nitride semiconductor materials

Abstract

A method and apparatus for growing low defect, optically transparent, colorless, crack-free, substantially flat, single crystal Group III nitride epitaxial layers with a thickness of at least 10 microns is provided. These layers can be grown on large area substrates comprised of Si, SiC, sapphire, GaN, AlN, GaAs, AlGaN and others. In one aspect, the crack-free Group III nitride layers are grown using a modified HVPE technique. If desired, the shape and the stress of Group III nitride layers can be controlled, thus allowing concave, convex and flat layers to be controllably grown. After the growth of the Group III nitride layer is complete, the substrate can be removed and the freestanding Group III nitride layer used as a seed for the growth of a boule of Group III nitride material. The boule can be sliced into individual wafers for use in the fabrication of a variety of semiconductor structures (e.g., HEMTs, LEDs, etc.).

1 . A freestanding AlN single crystal wafer that is crack-free, has a thickness of at least 100 microns, a diameter of at least 2 inches and a thermal conductivity greater than 3.2 W/K cm.  
   
   
       2 . The freestanding AlN single crystal wafer of  claim 1  having a thermal conductivity of about 3.3 W/K cm.  
   
   
       3 . The freestanding AlN single crystal wafer of  claim 1  having a defect density less than 10 7  cm −2 .  
   
   
       4 . The freestanding AlN single crystal wafer of  claim 1  being optically transparent.  
   
   
       5 . The freestanding AlN single crystal wafer of  claim 1  being colorless.  
   
   
       6 . The freestanding AlN single crystal wafer of  claim 1  having an optical absorption less than 5% at a wavelength of 280 nm.  
   
   
       7 . The freestanding AlN single crystal wafer of  claim 1  having an electrical resistivity at 300° K of at least 10 6  Ohm cm.  
   
   
       8 . The freestanding AlN single crystal wafer of  claim 1  having a full width half maximum of FWHM of the x-ray rocking curve measured in ω-scanning geometry is less than 700 arc seconds.  
   
   
       9 . The freestanding AlN single crystal wafer of  claim 1  being entirely crack-free as verified by transmission optical microscopy and reflection optical microscopy.  
   
   
       10 . A freestanding AlN single crystal wafer that is crack-free, has a thickness of at least 100 microns, a diameter of at least 2 inches and is optically transparent and colorless.  
   
   
       11 . The freestanding AlN single crystal wafer of  claim 10  having a thermal conductivity of about 3.3 W/K cm.  
   
   
       12 . The freestanding AlN single crystal wafer of  claim 10  having a defect density less than 10 7  cm −2    
   
   
       13 . The freestanding AlN single crystal wafer of  claim 10  having an optical absorption less than 5% at a wavelength of 280 nm.  
   
   
       14 . The freestanding AlN single crystal wafer of  claim 10  having an electrical resistivity at 300° K of at least 10 6  Ohm cm.  
   
   
       15 . The freestanding AlN single crystal wafer of  claim 10  having a full width half maximum of FWHM of the x-ray rocking curve measured in ω-scanning geometry is less than 700 arc seconds.  
   
   
       16 . The freestanding AlN single crystal wafer of  claim 10  being entirely crack-free as verified by transmission optical microscopy and reflection optical microscopy.  
   
   
       17 . A freestanding AlN single crystal wafer that is crack-free, optically transparent and colorless, the freestanding AlN single crystal having a thickness of at least 100 microns, a diameter of at least 2 inches, a thermal conductivity of about 3.2 W/K cm, an optical absorption less than 5% at a wavelength of 280 nm, an electrical resistivity of at least 10 6  Ohm cm at 300° K, and a full width half maximum of FWHM of the x-ray rocking curve measured in ω-scanning geometry less than 700 arc seconds.  
   
   
       18 . The freestanding AlN single crystal wafer of  claim 17  being entirely crack-free as verified by transmission optical microscopy and reflection optical microscopy.