Molecular beam epitaxial growth of GaAs/AlGaAs multiquantum well on germanium substrate

Abstract

We have addressed Molecular Beam Epitaxial (MBE) growth of GaAs/AlGaAs multi quantum well (MQW) structure on germanium (Ge) substrate. The growth mechanism includes deposition of a low-temperature (350°C) migration enhanced epitaxy (MEE) grown GaAs layer which was overgrown by a thin GaAs layer grown at low-temperature (475°C). The overgrown GaAs layer was annealed multiple times at 600°C during the growth. We believe the MEE layer and this special annealing scheme effectively blocked the dislocations at the GaAs/Ge interface from propagating into the top epitaxial layers. The morphological and optical properties of the samples were studied by Atomic Force Microscopy (AFM), Cross-sectional Transmission Electron Microscopy (XTEM) and Photoluminescence (PL) measurements respectively. The AFM shows a smooth surface with a root mean square (rms) roughness ~0.16nm which is of the same order to a control sample consisting of a similar MQW structure grown on GaAs substrate. Though some defects at the GaAs/Ge interface are clearly visible from XTEM, the TEM image of the QWs show that they are free from structural defects. From the PL spectra, distinctly sharp peaks are clearly visible for the QWs of different widths and the observed PL linewidth is comparable to that of the control sample.