Publications

X-ray topography characterization of gallium nitride substrates for power device development

Raghothamachar, Balaji; Liu, Yafei; Peng, Hongyu; Ailihumaer, Tuerxun; Dudley, Michael; Shahedipour-Sandvik, F.S.; Jones, Kenneth A.; Armstrong, Andrew A.; Allerman, A.A.; Han, Jung; Fu, Houqiang; Fu, Kai; Zhao, Yuji

Gallium nitride substrates grown by the hydride vapor phase epitaxy (HVPE) method using a patterned growth process have been characterized by synchrotron monochromatic beam X-ray topography in the grazing incidence geometry. Images reveal a starkly heterogeneous distribution of dislocations with areas as large as 0.3 mm2 containing threading dislocation densities below 103 cm−2 in between a grid of strain centers with higher threading dislocation densities (>104 cm−2). Basal plane dislocation densities in these areas are as low as 104 cm−2. By comparing the recorded images of dislocations with ray tracing simulations of expected dislocations in GaN, the Burgers vectors of the dislocations have been determined. The distribution of threading screw/mixed dislocations (TSDs/TMDs), threading edge dislocations (TEDs) and basal plane dislocations (BPDs) is discussed with implications for fabrication of power devices.