Structural and photoluminescence study of thin GaN film grown on silicon substrate by metalorganic chemical vapor deposition

GaN epitaxial layer was grown on Si(111) substrate by metalorganic chemical vapor deposition (MOCVD). The structure consists of 50 nm thick high-temperature grown AlN buffer layer, 150 nm thick AlGaN layer, 30 nm low-temperature grown AlN layer, 300 nm GaN layer, 50 nm AlGaN superlattice layer, followed by 100 nm GaN epitaxial layer. The low-temperature AlN interlayer and AlGaN superlattice layer were inserted as the defect-blocking layers in the MOCVD grown sample to eliminate the dislocations and improve the structural and optical properties of the GaN layer. The dislocation density at the top surface was decreased to ∼ 2.8 × 109/cm2. The optical quality was considerably improved. The photoluminescence emission at 3.42–3.45 eV is attributed to the recombination of free hole-to-donor electron. The observed 3.30 eV emission peak is assigned to be donor–acceptor transition with two longitudinal optical phonon side bands. The relationship of the peak energy and the temperature is discussed.