Real-Time Observation of Atomic Ordering in (001)In0.53Ga0.47AsEpitaxial Layers

We report the first real-time observation of atomic ordering in a semiconductor alloy during epitaxial growth. (001) ${\mathrm{In}}_{0.53}{\mathrm{Ga}}_{0.47}$As layers deposited below about 400 °C exhibit a strong anisotropy in the broadening parameters of the $E_1{,E}_1+{\Delta }_1$ transitions that is observable with reflectance-difference spectroscopy. This unusual optical behavior results from intraband mixing driven by triple-period ordering along both [111] and $\left[11\overline{1}\right]$ directions simultaneously. This microstructure is realizable with stoichiometry ${\mathrm{In}}_{0.556}{\mathrm{Ga}}_{0.444}\mathrm{As}$ virtually identical to that needed to lattice match InP.