InAs on InP:indermediate alloy formation and interface vibrations

We present a detailed investigation of the vibrational modes of single thin InAs layers directly grown on InP substrate. The Raman spectra have revealed the presence of features besides the longitudinal-optical and transverse-optical modes related to InP and InAs. We have succeeded in distinctly detecting Raman modes due to the presence of an intermixed InxAs1-xP layer resulting from an incorporation of arsenic in the InP substrate. Moreover, our Raman data show unusual intense features related to the lattice vibrations of interface bonds. The observed energies of these interface modes are in good agreement with the calculation based on a modulated dielectric model. This work clearly demonstrates that the vibrational properties of heterostructures can be sensitive to the structure of the interface and that Raman spectroscopy is a powerful tool to investigate the crystal structure of heterostructures as well as the interfacial chemistry.