Accommodation of strain in ultrathin InAs/GaAs films

X-ray standing-wave and extended x-ray-absorption fine-structure measurements have determined the strain and bond distortions in a buried InAs monolayer grown epitaxially on GaAs(001). The In atoms are found to reside 1.64±0.03 A above the last-As plane of the GaAs substrate with an In-As bond length of 2.57±0.02 A. Relative to bulk InAs, this corresponds to an 8% expansion in the In-As planar distance perpendicular to the interface and a 0.05-A compression in the In-As bond length. This experiment indicates that macroscopic-elastic theory describes the distortions in InAs/GaAs(001) films even in the monolayer limit