Optical constants of In[sub 0.53]Ga[sub 0.47]As/InP: Experiment and modeling.

The optical constants ∊(E)=∊[SUB1](E)+i∊[SUB2](E) of unintentionally doped In[SUB0.53]Ga[SUB0.47]As lattice matched to InP have been measured at 300 K using spectral ellipsometry in the range of 0.4 to 5.1 eV. The ∊ (E) spectra displayed distinct structures associated with critical points at E[SUB0] (direct gap), spin-orbit split E[SUB0]+Δ[SUB0] component, spin-orbit split E[SUB1], E[SUB1]+ Δ, E[SUP ′,SUB 0] feature, as well as E[SUB2]. The experimental data over the entire measured spectral range (after oxide removal) has been fit using the Holden model dielectric function [Holden et al., Phys. Rev. B 56, 4037 (1997)], plus a Kramers-Kronig consistent correction, described in this work, that improves the fitting at low energies. This extended model is based on the electronic energy-band structure near these critical points plus excitonic and band-to-band Coulomb-enhancement effects at E[SUB0], E[SUB0]+ Δ[SUB0], and the E[SUB1], E[SUB1] + Δ[SUB1], doublet. In addition to evaluating the energies of these various band-to-band critical points, information about the binding energy (R[SUB1]) of the two-dimensional exciton related to the E[SUB1], E[SUB1] +Δ[SUB1] critical points was obtained. The value of R[SUB1] was in good agreement with effective mass/k·p theory. The ability to evaluate R[SUB1] has important ramifications for first-principles band-structure calculations that include exciton effects at E[SUB0], E[SUB1], and E[SUB2] [M. Rohlfing and S. G. Louie, Phys. Rev. Lett. 81, 2312 (1998); S. Albrecht et al., Phys. Rev. Lett. 80, 4510 (1998)]. [ABSTRACT FROM AUTHOR]