Correlated and anti-correlated vertical self-organization of InAs quantum wires in InAs/InP stacked structures versus the spacer layer nature

Abstract

We address vertical self-organization of stacked InAs quantum island layers grown on InP(OO1) substrate using either InP or InAlAs as spacer layers. From AFM imaging we show that, whatever the spacer nature is, wire shaped islands are strongly favored by the stacking process. In contrast, transmission electron microscopy (TEM) studies indicate that the vertical arrangement is strongly dependent on the nature of the spacer layer. On the one hand, for InP spacers, crosssectional TEM images exhibit the well-known correlated vertical alignment of InAs wires usually explained by the strain field induced by buried islands. On the other hand, for InAlAs spacers, the stacking process gives rise to an anti-correlated vertical arrangement of the InAs wires. This anticorrelated arrangement is principally the result of a phase separation taking place in the InAlAs spacer layer. From photoluminescence measurements, we show how growth conditions should be chosen to improve the stacking process versus the vertical arrangement kind. For the correlated arrangement, we have to restrain the increase of the wire size during the stacking process. In contrast, for the anti-correlated arrangement, a relationship between the wire width and the spacer thickness ought to be fulfilled in order to avoid the coming out of wire missing rows responsible of a worsening of wire organization.