Spectroscopic ellipsometry for monitoring and control of molecular beam epitaxially grown HgCdTe heterostructures

A systematic study of the effect of measurement perturbation on in situ monitoring of the composition of molecular beam epitaxially (MBE) grown Hg1−xCdxTe using spectroscopic ellipsometry was carried out. Of the five variables investigated, which included angle of incidence, wavelength of the light beam, modulator rotation, analyzer rotation, and modulator amplitude, the angle of incidence and the modulator rotation had the strongest effect on the in situ Hg1−xCdxTe composition monitoring process. A wobble-free sample manipulator was installed to reduce the impact of these two variables. With these improvements, the spectroscopic ellipsometer is now routinely used to monitor Hg 1−xCdxTe compositions during MBE growth of heterostructures and is a useful tool in diagnosing growth-related problems. Examples are included for both application areas, that include the control of the interface between Hg1−xCdxTe layers of different compositions, i.e. device engineering.