Gas-source molecular-beam epitaxy of InGaP and GaAs on strained-relaxed GexSi1−x/Si

Abstract

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 ∼10 mW/cm2. The best dislocation density achieved was 5×106–107 cm−2 in the InGaP/GaAs/Ge/graded GeSi/Si structure.