Microstructural properties of GaN grown on a Si(110) substrate by gas-source molecular beam epitaxy: Dependence on the ammonia flux

• The surface flatness of GaN thin films was improved by increasing the ammonia (NH3) flux.
• The reduction of growth rate was observed as the NH3 flux increases.
• The crystalline quality of the GaN thin film grown under the high NH3 flux was degraded.
• The GaN grown under the high NH3 flux condition revealed high density of dislocations.

The microstructural properties of a GaN thin film grown on a Si(110) substrate under various ammonia (NH3)-flux conditions were observed to study growth mode and defect evolution. The surface flatness of GaN thin films was improved with the increase of the NH3 flux while the thickness was decreased by increasing the NH3 flux. In addition, the crystalline quality of the GaN film grown under the lower NH3 flux (100 sccm) was better than that of the film under the higher NH3 flux (400 sccm). The different dislocation behaviors depending on NH3 fluxes were observed; the low density of dislocations was measured and most of dislocations penetrating the thin film was mixed- and edge-type dislocations when GaN was grown under the low NH3 flux condition while the high density of dislocation and many mixed- and screw-type dislocations penetrating the film were observed in the GaN film grown under the high NH3 flux. These phenomena are demonstrated by using a kinetic model related to the role of NH3.