Thin film transmission matrix approach to fourier transform infrared analysis of HgCdTe multilayer heterostructures

The ability to achieve high-yield focal plane arrays from Hg1−xCdxTe molecular beam epitaxy material depends strongly on postgrowth wafer analysis. Nondestructive analysis that can determine layer thicknesses as well as alloy compositions is critical in providing run-to-run consistency. In this paper, we incorporate the use of a thin film transmission matrix model to analyze Fourier transform infrared (FTIR) transmission spectra. Our model uses a genetic algorithm along with a multidimensional, nonlinear minimization Nelder-Mead algorithm to determine the composition and thickness of each layer in the measured epitaxial structure. Once a solution has been found, the software is able to predict detector performance such as quantum efficiency and spectral response. We have verified our model by comparing detector spectral data to our predicted spectral data derived from the room-temperature FTIR transmission data. Furthermore, the model can be used to generate design curves for detectors with varying absorber thicknesses and/or different operating temperatures. The consequence of this are reduced cycle times and reduced design variations.

[1]  D. Marple,et al.  Refractive Index of ZnSe, ZnTe, and CdTe , 1964 .

[2]  E. Finkman,et al.  The exponential optical absorption band tail of Hg1−xCdxTe , 1984 .

[3]  P. Griffiths.  Fourier Transform Infrared Spectrometry , 2007 .

[4]  Valerie Randall,et al.  HgCdTe focal plane arrays for dual-color mid- and long-wavelength infrared detection , 2004 .

[5]  V. Garber,et al.  Monitoring HgCdTe layer uniformity by the differential absorption technique , 1996 .

[6]  John A. Nelder,et al.  A Simplex Method for Function Minimization , 1965, Comput. J..

[7]  S. Krishnamurthy,et al.  Near band edge absorption spectra of narrow‐gap III–V semiconductor alloys , 1996 .

[8]  Vaidya Nathan,et al.  HgCdTe/Si materials for long wavelength infrared detectors , 2004 .

[9]  P. Yeh,et al.  Optical Waves in Layered Media , 1988 .

[10]  Z. Kučera.  Dispersion of the refractive index of Hg1–xCdxTe , 1987 .

[11]  Peter R. Griffiths,et al.  Comprar Fourier Transform Infrared Spectrometry | James D. Winefordner | 9780471194040 | Wiley , 2007 .

[12]  M. Carmody,et al.  Determination of individual layer composition and thickness in multilayer HgCdTe structures , 2004 .

[13]  M. Carmody,et al.  Improved model for the analysis of FTIR transmission spectra from multilayer HgCdTe structures , 2005 .

[14]  M. Carmody,et al.  Optical-absorption model for molecular-beam epitaxy HgCdTe and application to infrared detector photoresponse , 2004 .

[15]  B. Jensen,et al.  Dispersion of the refractive index of InP and ZnTe , 1983 .

[16]  J. Schmit,et al.  Energy gap versus alloy composition and temperature in Hg1−xCdxTe , 1982 .