Optical functions of InGaP/GaAs epitaxial layers from 0.01 to 5.5 eV

In0.49Ga0.51P films, both undoped and doped n- and p-type (up to 10(18) cm(-3)), were grown lattice matched on GaAs substrates, with different miscut angles, by Metal-Organic Vapour Phase Epitaxy (MOVPE) at different temperatures. The shift of the fundamental gap Eo, caused by "ordering effect" was measured as a function of temperature by photoluminescence. The complex refractive index (n) over tilde = n + ik and the dielectric function (ε) over tilde = epsilon(1) + epsilon(2) at room temperature were determined from 0.01 to 5.5 eV by using complementary data from fast-Fourier-transform far-infrared (FFT-FIR), dispersive, and ellipsometric spectroscopies. The effect of the native oxide was accounted for and the self-consistency of the optical functions was checked in the framework of the Kramers-Kronig causality relations. In the restrahlen region the dielectric function was well fitted by classical Lorentz oscillators; in the transparent region below E-0, the refractive index was modelled by a Sellmeier dispersion relation; in the interband region the dielectric function was well reproduced by analytical lineshapes associated to seven critical points. Thus parametrized analytical expressions were obtained for the optical functions all over the spectral range, without discontinuities, to be used in the modelling and characterization of multi-layer structures, also on opaque substrates.