Interface of CuIn1-xGaxSe2/GaAs heterostructure

Misfit dislocations at the interface and a high density of threading dislocations initiated from the interface were observed in CuInSe2 epitaxial films grown on (001) GaAs substrates at 475 degrees C by a molecular beam epitaxy (MBE) technique. An epitaxial temperature as low as 300 degrees C was realized by photo-assisted MBE or atomic layer epitaxy technique. Microtwins were found in the films grown by low-temperature processes. The difference in defect types in the films grown at different temperatures is attributed to the temperature dependence on the release of misfit strain in the films. A lattice-matched CuIn0.3Ga0.7Se2/GaAs heterostructure grown at 520 degrees C eliminates dislocations and microtwins. High-resolution lattice images show a contrast change at about 3 nm in thickness at the interface. By comparing the lattice image with a simulated one, we conclude that interdiffusion occurs during film growth.