Role of AlxGa1-xAs buffer layer in heterogeneous integration of GaAs/Ge

The material and optical properties of the GaAs/AlxGa1-xAs/Ge structures grown by metalorganic chemical vapor deposition were examined and found to be dependent of the Al content x. SIMS and PL measurements show that the 10 nm AlxGa1-xAs buffer layer with x = 0.3 and 0.6 are equally effective in suppressing the outdiffusion of Ge, whereas x = 1.0 gives the most abrupt interface. The best morphology with surface rms of 0.3 nm is obtained in the structure with x = 0.3 buffer layer. Analysis on change of strain in the AlxGa1-xAs buffer layer suggests that the compressive strain at the AlxGa1-xAs-GaAs interface is compensated by the tensile strain at the Ge-AlxGa1-xAs interface when x similar to 0.3. AlxGa1-xAs lattice matched to Ge is crucial for better result in surface morphology, but higher Al content is preferred for eliminating the interdiffusion of atoms at the heterointerface. (C) 2011 American Institute of Physics. [doi:10.1063/1.3561489]