Ordering structure along the [001] direction of InAlAs

Abstract We have found a new type ordering structure in materials containing Indium. Generally conventional natural superlattice (NSL) stacks toward to { 1 1 1 } . However, the periodical structure in question stacks along the [ 0 0 1 ] direction, sometimes parallel to the substrate. We have studied the structure in detail as seen in InAlAs-bulk layers on a vicinal ( 0 0 1 ) InP substrate. We investigated the structure using a transmission electron microscope and a high-resolution X-ray diffraction method, and confirmed the structure stacks along [ 0 0 1 ] direction with a pitch three times that of the InP lattice constant. We found a similar structure in InAlGaP-bulk layers on a ( 1 0 0 ) GaAs substrate 10 ∘ tilted toward the 〈 0 1 1 〉 direction. The mechanisms have not been clarified yet, however, we consider that atomic steps on the epitaxial surface could be related.