Fig. 1: Crystal growth of FeAs/InAs SL structures.

a Schematic sample structure of the FeAs/InAs SL grown on a GaAs (001) substrate. There are N FeAs layers (red planes) embedded in an InAs matrix with a regular distance of tInAs. The total thickness of the FeAs/InAs structures is 41–47 MLs (= 12.4–14 nm). b In situ RHEED patterns along the [\(\bar{1}\)10] direction during the growth of the FeAs/InAs SL in sample A4. c High-resolution scanning TEM of a sample with 1 ML FeAs embedded in InAs (left panel) and the corresponding mapping of Fe atoms by EDX (right panel). d Fe distribution along the growth direction mapped with EDX, which follows a normal distribution with a standard deviation of 0.45 nm (1.5 ML of InAs).