HgCdTe Growth on 6 cm × 6 cm CdZnTe Substrates for Large-Format Dual-Band Infrared Focal-Plane Arrays
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This paper describes molecular-beam epitaxy growth of mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) dual-band device structures on large-area (6 cm × 6 cm) CdZnTe substrates. Wafer-level composition and defect mapping techniques were used to investigate the limiting mechanisms in improving the cutoff wavelength (λc) uniformity and reducing the defect density. Structural quality of epitaxial layers was monitored using etch pit density (EPD) measurements at various depths in the epitaxial layers. Finally, 640 × 480, 20-μm-pixel-pitch dual-band focal-plane arrays (FPAs) were fabricated to demonstrate the overall maturity of growth and fabrication processes of epitaxial layers. The MWIR/LWIR dual-band layers, at optimized growth conditions, show a λc variation of ±0.15 μm across a 6 cm × 6 cm CdZnTe substrate, a uniform low macrodefect density with an average of 1000 cm−2, and an average EPD of 1.5 × 105 cm−2. FPAs fabricated using these layers show band 1 (MWIR) noise equivalent temperature difference (NETD) operability of 99.94% and band 2 (LWIR) NETD operability of 99.2%, which are among the highest reported to date.
KeywordsCrystal growth defects detector molecular-beam epitaxy optical characterization optoelectronic materials photovoltaic materials II-VI semiconductors CdZnTe HgCdTe
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- 2.D.F. King, W.A. Radford, E.A. Patten, R.W. Graham, T.F. McEwan, J.G. Vodicka, R.E. Bornfreund, P.M. Goetz, G.M. Venzor, S.M. Johnson, J.E. Jensen, B.Z. Nosho, and J.A. Roth, Proc. SPIE 6206, 62060W-1 (2006).Google Scholar