Low defect density bulk AlN substrates for high performance electronics and optoelectronics

Using the physical vapor transport (PVT) method, single crystal boules of AlN have been grown and wafers sliced from them have been characterized by synchrotron white beam X-ray topography (SWBXT) in conjunction with optical microscopy. X-ray topographs reveal that the wafers contain dislocations that are inhomogeneously distributed with densities varying from as low as 0 cm ^-2 to as high as 10⁴ cm^-2. Two types of dislocations have been identified: basal plane dislocations and threading dislocations, both having Burgers vectors of type 1/3<1120> indicating that their origin is likely due to post-growth deformation. In some cases, the dislocations are arranged in low angle grain boundaries. However, large areas of the wafers are nearly dislocation-free and section X-ray topographs of these regions reveal the high crystalline perfection.