Broadening of interband resonances in thin AlAs barriers embedded in GaAs

Abstract

AlAs barriers embedded in GaAs were studied by spectroscopic ellipsometry and resonant Raman scattering. Heterostructures with AlAs barrier widths ranging from 2 to 30 nm were grown by molecular-beam epitaxy at growth temperatures between 410 and 660 Degree C. For layer widths below 10 nm the E(ind 1) and E(ind 1)+ Delta(ind 1) critical point resonance in the dielectric function of the AlAs was found to broaden and to be smeared out completely for a width of 2 nm. Resonant Raman scattering by the AlAs LO phonon reveals for layer widths equal or smaller than 10 nm a considerable broadening of also the E(ind 0) interband transition in the AlAs. The magnitude of the critical point broadening and redistribution of oscillator strength, however, was found to be independent of the growth temperature and thus of the cation intermixing observed by Raman spectroscopy for growth temperatures equal or greater than 600 Degree øC. Therefore, the observed critical point broadening is not caused by th e formation of graded composition (AlGa)As barriers. Instead, the broadening of interband resonances is attributed to a spread of the carrier wave functions into the surrounding GaAs, which are not confined within the AlAs barrier for neither the E(ind 0) nor the E(ind 1) and E (ind 1) + Delta(ind 1) interband transitions

Interfacial intermixing and arsenic incorporation in thin InP barriers embedded in In0.53Ga0.47As

“…This is in contrast to AlAs barrier layers embedded in GaAs, for which a complete disappearance of the E 1 /E 1 ϩ⌬ 1 critical-point resonance was found for barrier widths Ͻ5 nm, even in the absence of any detectable cation intermixing. 6 The energy down shift of the E 1 /E 1 ϩ⌬ 1 interband resonance as well as the frequency down shift of the InP LO phonon ͑see Fig. 2͒ observed for InP barrier widths у10 nm, for which effects due to the intermixed interface layers are expected to be less prominent, can be explained by a constant incorporation of As, and possibly also Ga, into the InP barrier layers.…”

“…5,6 Within the multilayer model the InP substrate and the In 0.53 Ga 0.47 As layers were represented by bulk dielectric functions. 9 The dielectric function of the InP barrier layers was fitted using a parametric model, which is based on an oscillator ensemble to describe critical-point structures.…”

“…5,6 In the present study, we investigated single InP barrier layers embedded in In 0.53 Ga 0.47 As, which served as test structures for the growth of InP barriers in ͑InGa͒As MQW and in transistor structures. Raman spectroscopy in combination with spectroscopic ellipsometry allowed us to distinguish between interfacial intermixing, resulting in ͑InGa͒͑AsP͒ interface layers about 2 nm in thickness, and the incorporation of As into the InP at a constant concentration for InP layer thicknesses up to at least 20 nm.…”

In-plane optical anisotropy of InAs/GaSb superlattices with alternate interfaces

“…As a result, the optical properties along the [110] and [1$\overline{1}$0] directions are different. In the RDS spectra, InSb features were not observed clearly in room temperature, since the features of E 0 , E 1 , and E 1 + Δ 1 CPs are very broadening with few ML [24]. This effect is identified as the spread of carrier wave function of the ultra-thin IF to surrounding layers.…”

Spectroscopic ellipsometry for characterization of InAs/Ga1−xInxSb superlattices

“…[6][7][8][9] Further, SE allows also the real-time in situ control of epitaxial layer growth. [10][11][12][13] For the analysis of semiconductor heterostructures, fitting procedures based on the bulk dielectric functions of the heterostructure constituents have been used to extract information on layer thickness and composition from the pseudodielectric function measured by SE.…”