Influence of AlN buffer growth conditions on crack formation and crystalline quality of GaN grown on 6-inch Si(111)

GaN-on-Si epitaxy is attractive for high-power and high-frequency devices, but lattice and thermal mismatches can lead to cracking, residual tensile stress, and high threading dislocation densities. This work investigates the influence of AlN growth conditions on GaN grown on 6-inch Si(111) substrates using a single-AlN/single-AlGaN buffer architecture. At a fixed AlN growth time of 30 min, growth at a V/III ratio of 5100 was associated with a lower apparent growth rate and a thinner AlN buffer than growth at a V/III ratio of 1020. Atomic force microscopy suggested differences in the size and distribution of island-like features on the AlN surfaces. In situ reflectance indicated earlier surface planarization and more stable subsequent growth for the structure prepared with the higher AlN V/III ratio. The resulting GaN film showed no discernible cracks or pits in the reported SEM field of view and exhibited the lowest Raman-derived residual tensile stress among the investigated samples, at 0.207 GPa. The corresponding screw and edge threading-dislocation-density estimates derived from X-ray rocking curves were 1.15 × 10 9 and 8.92 × 10 9 cm −2 , respectively. Narrower high-resolution X-ray diffraction rocking curves and lower dislocation-density estimates further indicated improved crystalline quality. These results highlight the role of AlN growth conditions in improving GaN film quality within a single-AlN/single-AlGaN buffer architecture.