Atomic‐scale structure of InAs/InAs_1−xSb_x superlattices grown by modulated molecular beam epitaxy Available to Purchase

We present cross‐sectional scanning tunneling microscopy (STM) studies of the atomic‐scale structural and electronic properties of InAs/InAs_1−xSb_x superlattices grown by modulated molecular‐beam epitaxy. In this technique the Group V composition is controlled by rapid modulation of the Group V beams rather than adjustment of the Group V flux ratios. A superlattice sample was grown at 475 °C consisting of 52 Å InAs_1−xSb_x alternating with 172 Å InAs for 30 periods on a GaSb (001) substrate. The InAs_1−xSb_x alloy layers consisted nominally of 7.8 Å InAs alternating with 5.2 Å InSb for four periods. X‐ray diffraction was used to determine an average composition of InAs_0.76Sb_0.24 for the alloy layers. Constant‐current STM images of the superlattice exhibit clear, electronically induced contrast between the InAs layers and InAs_0.76Sb_0.24 layers, and also reveal ordering within the InAs_0.76Sb_0.24 layers. Interfaces between the InAs layers and the InAs_0.76Sb_0.24 layers appear sharp, though there is evidence of more atomic intermixing at the InAs‐on‐InAs_0.76Sb_0.24 interface. Significant variation in composition within individual InAs_0.76Sb_0.24 alloy layers and apparent Sb incorporation from the InAs_0.76Sb_0.24 layers into the surrounding InAs layers are also observed.