| AVS 54th International Symposium | |
| Electronic Materials and Processing | Monday Sessions |
| Session EM+NS-MoA |
| Session: | Semiconductor Nanostructures for Electronics and Optoelectronics I |
| Presenter: | C. Dion, École Polytechnique de Montréal, Canada |
| Authors: | C. Dion, École Polytechnique de Montréal, Canada P. Desjardins, École Polytechnique de Montréal, Canada N. Shtinkov, Université d'Ottawa, Canada M.D. Robertson, Acadia University, Canada F. Schiettekatte, Université de Montréal, Canada P.J. Poole, National Research Council, Canada S. Raymond, National Research Council, Canada |
| Correspondent: | Click to Email |
The formation of atomically sharp interfaces during the epitaxial growth of heterojunctions is a challenging task since atomic intermixing between the different materials is often unavoidable due to the relatively high growth temperatures involved. This effect has been found to be particularly important during the growth of self-assembled quantum dots (QDs) for which evidence of highly alloyed structures have been reported by several authors for a wide variety of semiconductor systems.1 In the present work, we investigate intermixing during the growth of self-assembled InAs/InP QDs by chemical beam epitaxy. Using a careful combination of photoluminescence (PL) and transmission electron microscopy (TEM) measurements as well as tight-binding (TB) calculations, we have devised a procedure that enables an unambiguous assignment of QD heights (hQD) and composition to the observed PL transitions. PL spectra from ensembles of QDs are characterized by distinctive peaks which can be attributed to the ground state emission of QD families having the same thickness in terms of an integer number of monolayers (ML).2 Consequently, QDs electronic transitions are analogous to those of quantum wells and can be analyzed accordingly. TB calculations were performed by assuming (i) InP/InAs1-xPx/InP structures of varying P concentration ([P]) with abrupt interfaces and (ii) InP/InAs/InP structures with P diffusion concentration profiles described by the diffusion length LD. Both calculation frameworks lead to similar, realistic descriptions of the as-grown material. However, the above procedure yielded two solutions sets of (hQD : [P] or LD) compatible with experimental results. In order to determine which solution set is the most suitable, they were used as input data in a Bloch-wave simulation of TEM image contrast providing a sequence of contrasts versus hQD. A unique solution set was compatible with observed TEM data, therefore allowing an unambiguous assignment of hQD and [P] to the observed PL transitions. For the samples under investigation, it was concluded that the electronic transitions can be best attributed to a 3 ML-thick wetting layer and 4 to 13 ML-thick QDs with a relatively constant [P] of 10 ± 1 %.
1 N. Liu, et al., Phys. Rev. Lett. 84, 334 (2000).
2 S. Raymond, et al., Semicond. Sci. Technol. 18, 385 (2003).