Interfacial roughness in InAs/GaAs heterostructures determined by soft x-ray reflectivity

X-ray reflectivity has been used to determine interfacial roughness of as-grown 250-Å-thick InAs overlayers deposited on GaAs substrates by molecular-beam epitaxy under differing growth and substrate conditions. Results indicate that in each case the top surface was smooth, but that the buried interface separating these highly lattice-mismatched materials exhibits root-mean-square roughness parameters in the range of 10-19 Å. As-stabilized growth produced the roughest InAs-GaAs (buried) interface, while In-stabilized growth on a slightly misoriented substrate produced the smoothest InAs-GaAs interface.