SPECTROSCOPIC ELLIPSOMETRY APPLIED FOR IN-SITU CONTROL OF LATTICE-MATCHED III-V GROWTH IN MOVPE

Stoichiometry control of lattice matched compound semiconductors durin g growth is still a challenge for in situ optical techniques. This is because the energy shifts of the semiconductor optical gap induced by strain and stoichiometry compensate one another. Thus conventional cri tical point analysis for composition measurement is practically imposs ible. The remaining response of the measured ellipsometric parameters is very small but can be resolved when the signal-to-noise ratio of th e ellipsometer is sufficiently high. We exploit this for the closed-lo op control of InxGa1-xAs growth on InP where the trimethylindium (TMIn ) flux was directly controlled by the measured optical response in ord er to reach the desired lattice matched composition (x = 0.53). Es-sit u X-ray diffraction analysis verified ellipsometrically controlled lat tice matched growth. (C) 1998 Elsevier Science S.A.