Transmission electron microscopy study on defect reduction in GaAs on Si heteroepitaxial layers grown by metalorganic vapor phase epitaxy

Systematic transmission electron microscopy (TEM) investigations on defect configurations in heteroepitaxial GaAs on Si grown by metalorganic vapor phase epitaxy (MOVPE) are reported. The GaAs layers were deposited on Si by the conventional two-step growth mode. By introducing a thin (AlGa)As layer between the low-temperature and the high-temperature GaAs layer, a significant reduction of the dislocation density in the upper GaAs layer is observed after thermal-cycle (TC) annealing. The characteristics of dislocations in both as-grown and TC-annealed wafers are analyzed. The effect of TC annealing and the role of the (AlGa)As interlayer in combination with the TC-annealing process in the reduction of the defect density are discussed on the basis of the TEM observations.