ABSTRACT
Growth of Gallium nitride (GaN) layers by molecular beam epitaxy (MBE) may lead to the formation of polycrystalline layers. The analysis of the microstructure of the layers is performed by transmission electron microscopy and correlation with photoluminescence emission is carried out. This chapter provides microstructure analysis in order to determine the possible correlation between the characteristics of the microstructure and the photoluminescence emission. A GaN layer grown on a sapphire substrate leads to compressive strain during the cooling from the growth temperature. It results in a shift of the exciton energy towards higher energy. On a quartz substrate the opposite situation is expected, the GaN layer is under tensile strain and a lower energy shift occurs. The effect of the polycrystalline nature of the GaN layer was observed. The polycrystalline GaN layers obtained by NH3-MBE and electron cyclotron resonance-MBE growth contain the same defects as for the Metalorganic vapor phase epitaxy layers, stacking faults and inversion domain boundaries.
