Evidence For Interface Terraces In Ge/si Quantum Wells Obtained By Raman Scattering

We show that the change of the laser energy induces a frequency shift and broadening of the Ge-Ge resonant Raman line in Ge5Si5/Si QWs. This is explained by the existence of interfacial terraces, a conclusion supported by the study of QWs of different multiplicities: (i) The Ge-Si line broadens with QW multiplicity suggesting a wider distribution of terraces with increasing number of QWs. (ii) The Ge-Ge vibration is confined and does not propagate into the Si barrier, its line width and frequency depends on the QW width and therefore on the QWs multiplicity. (iii) The number of QWs affects the confined electronic states.219-2201-4502504Gammon, D., Shamabrook, B.V., Katzer, D.S., (1991) Phys. Rev. Lett., 67, p. 1547Grant, J., Menéndez, J., Pinczuk, A., Pfeiffer, L.N., West, K.W., Molinari, E., Baroni, S., (1991) Appl. Phys. Lett., 59, p. 2859Jusserand, B., (1990) Phys. Rev. B, 42, p. 7256Jusserand, B., Mollt, F., Molinari, E., Baroni, S., (1992) Surf. Sci., 267, p. 171Alonso, M.I., Cerdeira, F., Niles, D., Cardona, M., Kasper, E., Kibbel, H., (1989) J. Appl. Phys., 66, p. 5645De Gironcoli, S., Molinari, E., Schorer, R., Abstreiter, G., (1993) Phys. Rev. B, 48, p. 8959. , and references thereinDe Gironcoli, S., Baroni, S., (1992) Proc. XXI Int. Conf. on the Physics of Semiconductors, p. 109. , Beijing, China, 1992, eds. Ping Jiang and Hou-Zhi Zheng (World Scientific, Singapore) and references thereinDe Gironcoli, S., Molinari, E., (1994) Solid State Electronics, 37, p. 621Schorer, R., Abstreiter, G., De Gironcoli, S., Molinari, E., Kibbel, H., Presting, H., (1994) Phys. Rev. B, 49, p. 5406Brasil, M.J.S.P., Nahory, R.E., Tamargo, M.C., Schwarz, S.A., (1993) Appl. Phys. Lett., 63, p. 2688Hull, R., Bean, J.C., (1991) Semiconductors and Semimetals, 33, p. 1. , ed. T.P. Pearsall (Academic Press, New York)Rodrigues, P.A.M., Araújo Silva, M.A., Cerdeira, F., Bean, J.C., (1993) Phys. Rev. B, 48, p. 18024not