An X-ray standing wave study of ultrathin InAs films in GaAs(0 0 1) grown by atomic layer epitaxy

Abstract

X-ray standing wave and X-ray diffraction measurements were used to determine the structure of nominal 1 monolayer and 1/2 monolayer InAs films buried in GaAs(0 0 1). The films were grown by atomic layer epitaxy using trimethylgallium, tertiarybutylarsine and trimethylindium. For the full monolayer sample the standing wave measurement shows that the indium atoms reside 1.577±0.014 Å above the GaAs(0 0 4) substrate planes. A calculation based on the macroscopic elastic theory suggests that this corresponds to a single In x Ga 1− x As layer with x=0.794±0.068. The coherent fraction of 0.766±0.051 indicates a reasonably abrupt interface, as confirmed by the In-excitonic photoluminescence full width at half maximum of 5.74±0.01 meV. The half monolayer sample is less strained, as expected, with the indium atoms at 1.502±0.030 Å above the substrate planes, corresponding to an In x Ga 1− x As layer with x=0.446±0.145, and a coherent fraction of 0.88±0.12. This study exemplifies the complimentary nature of XSW and XRD.