Spectroscopic ellipsometry study of InGaAs alloy films grown on InP

We report pseudodielectric functions < epsilon > of InxGa1-xAs alloy films for In compositions x of 0 less than or equal to x less than or equal to0.66. Films were grown on (110) InP substrates by a solid-source molecular beam epitaxy. We used chemical etching to obtain the best approximation to the bulk pure dielectric responses epsilon of the films by removingg overlayers. We obtain the dependences of the E-1 and E-1 + Delta (1) band gaps with x, and estimated bowing parameters by fitting critical point structures in second energy derivatives of the < epsilon > spectra.