Existence of a CuAu-I-type ordered structure in lattice-mismatched InxGa1-xAs/InyAl1-yAs multiple quantum wells

Selected area electron diffraction pattern (SADP) and transmission electron microscopy (TEM) measurements were carried out to investigate the ordered structures in lattice-mismatched InxGa1-xAs/InyAl1-yAs multiple quantum wells (MQWs). The SADP showed two sets of extra spots with asymmetrical intensity, and the high-resolution TEM image showed doublet periodicity in the contrast of the (001) lattice planes. The results of the SADP and the TEM measurements showed that a CuAu-I-type ordered structure was observed near the lattice-mismatched InxGa1-xAs/InyAl1-yAs heterointerfaces. This CuAu-I-type ordered structure had an antiphase boundary in the periodically regular InxGa1-xAs/InyAl1-yAs lattice-mismatched region. The existence of a CuAu-I-type ordered structure in InxGa1-xAs/InyAl1-yAs MQWs might originate from the lattice mismatch between the InxGa1-xAs and the InyAl1-yAs layers. These results provide important information on the microstructural properties for improving operating efficiencies in long-wavelength optoelectronic devices, such as strain compensated electroabsorption modulators utilizing lattice-mismatched InxGa1-xAs/InyAl1-yAs MQWs. (C) 2001 American Institute of Physics.