Effects of ion bombardment on interband cascade laser structures

We report a preliminary investigation of ion bombardment (IB) effects on interband cascade laser (ICL) properties. Under some conditions, IB almost completely suppresses the vertical transport through a broad-area laser, although other times only a partial or negligible suppression is observed. To elucidate the mechanism that induces the suppression and in what part of the structure it occurs, we investigated the effects of IB on samples containing only ICL sub-regions. While IB increased the resistivity of a lightly-n-doped GaSb layer such as that used as a top or bottom separate confinement layer in an ICL, that layer was still much too conductive to strongly suppress the current flowing through a full device. The voltage drop was larger following IB of an InAs-AlSb superlattice such as that used in the top and bottom optical cladding layers in an ICL, although the effect was not large enough to fully account for the strong net suppression. And finally, the resistivity of an interband cascade LED containing the same active stages as an ICL was actually found to decrease following IB. Despite the inconclusive and sometime inconsistent findings of this study, it is nonetheless clear that if the effects can be controlled reproducibly, IB may provide a valuable tool for enhancing such ICL device configurations as weakly-index-guided narrow ridges and interband cascade vertical-cavity surface-emitting laser mesas that inject current and emit light only within a small central aperture.