Influence of substrate nitridation on the threading dislocation density of GaN grown on 200 mm Si (111) substrate.

Abstract High quality GaN was grown on 200 mm Si (111) substrates by using AlN and 3 step-graded Al x Ga 1-x N as the buffer layer in a metalorganic chemical vapor deposition system. We have investigated the influence of NH 3 pre-flow time on the threading dislocation density (TDD) of AlN, AlGaN buffer layers and GaN layers. It was observed that the compressive stress introduced into the buffer layer and GaN is dependent on the nitridation time. The lowest TDD for GaN obtained in our samples was ~1 × 109 cm−2 for screw type and 3.2 × 109 cm−2 for edge type dislocations, as obtained from atomic force microscopy and further confirmed by high resolution X-ray diffraction analysis. The threading dislocations generated in the first buffer layer (AlN) during its nucleation are found to influence the TDD in the subsequent layers. Samples without an intentional nitridation step exhibit higher TDD compared to the samples with optimal nitridation time. Longer nitridation time also leads to poor crystalline quality likely because of amorphous SiN x formation at the interface. Highlights • Wafer scale MOCVD growth of high-quality GaN on 200 mm Si (111) substrates. • Substrate nitridation (NH 3 pre-flow) controls crystallinity in each nitride layer. • Compressive stress in AlGaN depends on AlN quality which determines final wafer bow. • (Screw + mixed) type TDD of ~1 × 109 cm−2 & edge type TDD of 3.2 × 109 cm−2 are achieved. [ABSTRACT FROM AUTHOR]