Structure and interfacial stability of (111)-oriented InAsSb/InAs strained-layer multiquantum well structures

Biaxially strained InAs_xSb_1-x/InAs (111)-oriented multiquantum well structures with x≈0.8 have been grown by metalorganic vapor phase epitaxy. The quality of the multiquantum well structures was assessed by double-crystal x-ray diffraction (θ-2θ scans) and kinematical computer simulations. The x-ray diffraction pattern of an InAs_0.79Sb_0.21 /InAs multiquantum well film showed eight orders of satellite peaks, with a low diffuse background, indicating that excellent (111)-oriented structures can be achieved. The simulations modeled the compositional broadening of the interfaces, layer thickness fluctuations, and lattice spacing fluctuations of the compositionally modulated structures. The simulations indicated that the InAs/InAsSb interfaces were compositionally broadened over at least 0.5 nm, and that the layer thickness fluctuations of the highest quality structure were below the detection limit of 0.1 nm. Segregation of the antimony during deposition appears to be the primary cause of the compositional broadening. Simulations indicated that the layer thickness fluctuations increased with deposition rate, from less than 0.1 nm at a deposition rate of 8.4 nm/min to 1.2 nm at a deposition rate of 24 nm/min. The increase in the interface roughness was attributed to changes in surface reaction kinetics due to a shift in the III/V ratio at higher growth rates.