ELLIPSOMETRIC CHARACTERIZATION OF IN0.52AL0.48AS AND OF MODULATION DOPED FIELD-EFFECT TRANSISTOR STRUCTURES ON INP SUBSTRATES

The dielectric function of a thick layer of In0.52Al0.48As lattice matched to InP was measured by variable angle spectroscopic ellipsometry in the range 1.9-4.1 eV. The In0.52Al0.48As was protected from oxidation using a thin In0.53Ga0.47As cap that was mathematically removed for the dielectric function estimate. The In0.52Al0.48As dielectric function was then verified by ellipsometric measurements of other In0.53Ga0.47As/In0.52Al0.48As structures, including modulation doped field effect transistors (MODFET), and is shown to provide accurate structure layer thicknesses.