Atomic arrangements of a CuAu-I type ordered structure in strained InxGa1 − xAs/InyAl1 − yAs multiple quantum wells

Abstract

Many investigations on ordered phases in various III–V ternary compound semiconductor epilayers have been performed during past many years [1–10]. Among the various kinds of the ordering structures, a CuPttype superstructure has been the most extensively studied structures in III–V ternary semiconductors [1– 10]. However, relatively little work has been done on the CuAu-I type ordering in comparison with a CuPt-type ordering [11]. An existence of the CuAuI type ordering in the lattice-mismatched quantum wells provides an important physical information in achieving high efficiencies for optoelectronic devices. Even though some works concerning existence of a CuAu-I-type ordered structure in lattice-mismatched Inx Ga1−x As/InyAl1−yAs multiple quantum wells have been performed [11], studies concerning the atomic arrangements of a CuAu-I type ordered structure in lattice-mismatched Inx Ga1−x As/InyAl1−yAs multiple quantum wells (MQWs) are still important for understanding their detailed microstructural properties. Furthermore, lattice matched and lattice-mismatched Inx Ga1−x As/InyAl1−yAs quantum structures have been particularly attractive because of the considerable interest in both investigations of fundamental physical properties and fabrications of optoelectronic devices operating in the long wavelength spectral region [12– 16]. This paper reports atomic arrangements of a CuAu-I type ordered structure in lattice mismatched Inx Ga1−x As/InyAl1−yAs MQWs grown by molecular beam epitaxy (MBE). Selected area electron diffraction pattern (SADP) measurements were performed in order to investigate the atomic and the ordered structures of lattice matched and lattice mismatched Inx Ga1−x As/InyAl1−yAs MQWs.