CHARACTERIZATION OF MULTILAYER HGCDTE HETEROSTRUCTURES BY DIFFERENTIAL ABSORPTION-SPECTROSCOPY

In this work, we apply differential absorption spectroscopy to charact erization of multilayer epitaxial HgCdTe samples. Transmission of the sample is measured at room temperature and data filtering is applied t o remove noise and interference fringes. We use the spectrum of the in terference fringes to estimate the thickness of individual HgCdTe laye rs. The absorption coefficient is extracted from transmission and diff erentiated twice with respect to the photon energy, which allows us to determine the band gap of each of the layers. The accuracy of the dif ferential absorption procedure applied to multilayer structures appear s to be lower than for single-layer samples. Nevertheless, differentia l absorption spectroscopy is simple, nondestructive, and applicable at room temperature; consequently, it seems suitable for routine charact erization of multilayer HgCdTe wafers. (C) 1997 American Institute of Physics.