Spectroscopic ellipsometry characterization of Interface reactivity in GaAs-based superlattices

Pseudodielectric function spectra of GaAs/GaSb1-xAsy, GaSb/GaAsySb1-y and GaAs/GaPyAs1-y superlattices have been measured by spectroscopic ellipsometry in the 0.75-5.5 eV photon energy range. The analysis of the E-1 interband critical point and modeling of spectra has been carried out to investigate the chemistry of the anion exchange reaction and abruptness of interface composition in the superlattices. It has been found that a ternary compound GaPyAs1-y forms in the case of the P-for-As anion exchange reaction. In the case of As-for-Sb anion exchange reaction for (GaSb/GaAsySb1-y)(20) SLs, SE data show that this anion exchange results in the formation not only of a ternary alloy GaAsySb1-y but also in the formation of isoelectronic compounds AsSbx that segregate at the GaSb/GaAs interface. In the case of Sb-for-As anion exchange for (GaAs/GaSbyAs(1-y))(20) SLs, Sb segregates at the GaAs surface.