Characterization of multilayer HgCdTe heterostructures by differential absorption spectroscopy

Abstract

In this work, we apply differential absorption spectroscopy to characterization of multilayer epitaxial HgCdTe samples. Transmission of the sample is measured at room temperature and data filtering is applied to remove noise and interference fringes. We use the spectrum of the interference fringes to estimate the thickness of individual HgCdTe layers. The absorption coefficient is extracted from transmission and differentiated twice with respect to the photon energy, which allows us to determine the band gap of each of the layers. The accuracy of the differential absorption procedure applied to multilayer structures appears to be lower than for single-layer samples. Nevertheless, differential absorption spectroscopy is simple, nondestructive, and applicable at room temperature; consequently, it seems suitable for routine characterization of multilayer HgCdTe wafers. © 1997 American Institute of Physics.