GAS-SOURCE MOLECULAR-BEAM EPITAXY OF INGAP AND GAAS ON STRAINED-RELAXED GEXSI1-X/SI

Lattice-matched GaAs and InGaP structures on strain-relieved Ge/graded GeSi/Si without increasing the threading dislocation density at the III-V/Ge interface have been successfully grown. The results show that exposure of the Ge surface to As2 produces a drastic change in the step structure of the Ge surface. Subsequent exposure to Ga and continuation of growth invariably produces three-dimensional growth and a high threading dislocation density at the GaAs/Ge interface. However, exposure of the Ge surface to Ga does not appear to change the Ge step structure, and subsequent growth of GaAs leads to near two-dimensional growth and no massive increase in threading dislocation density at the GaAs/Ge interface as in the case of AS2 exposure. InGaP light-emitting homojunction diodes have been fabricated on the relaxed Ge/graded GeSi/Si. Room-temperature operation was achieved with a surface-emitting output power of approximately 10 mW/cm2. The best dislocation density achieved was 5 X 10(6)-10(7) CM-2 in the InGaP/GaAs/Ge/graded GeSi/Si structure.