Unintentional As incorporation into AlSb and interfacial layers within InAs/AlSb superlattices

The InAs/AlSb material system has proven to be an excellent choice for high-performance mid-infrared quantum cascade lasers. In this work, an unintentional displacement of Sb by residual As flux incident on the wafer was studied by direct monitoring of such flux during a simulated molecular beam epitaxy (MBE) growth sequence and dynamical simulations of high-resolution x-ray diffraction data collected on InAs/AlSb periodic structures grown under similar conditions. The results revealed that predominantly Al-As bonds detected at the InAs/AlSb interfaces, which were reported earlier, can be attributed to a residual bypass As flux on the wafer after closing the As shutter. Moreover, the experiments revealed that under typical growth conditions, AlSb binary barriers are converted into AlAsSb ternary layers with appreciable As content. The exact As content in the barriers is proportional to the effective As flux bypassing the closed shutter and thus depends on the particulars of the MBE system design and the exact As flux used for the growth of InAs wells. Published by the AVS.