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Middle wave infrared (MWIR) HgCdTe p-on-n double-layer heterojunctions (DLHJs) for infrared detector applications have been grown on 100-mm Si (112) substrates by molecular beam epitaxy (MBE) for large format 2,560 ϫ 512 focal plane arrays (FPAs). In order to meet the performance requirements needed for these FPAs, cutoff and doping uniformity across the 100-mm wafer are crucial. Reflection high-energy electron diffraction (RHEED), secondary ion mass spectrometry (SIMS), Fourier transform infrared spectrometry (FTIR), x-ray, and etch pit density (EPD) were monitored to assess the reproducibility, uniformity, and quality of detector material grown. Material properties demonstrated include x-ray full width half maximum (FWHM) as low as 64 arc-sec, typical etch pit densities in mid-10 6 cm Ϫ2 , cutoff uniformity below 5% across the full wafer, and typical density of macrodefects Ͻ 1000 cm Ϫ2 . The detector quality was established by using test structure arrays (TSAs), which include miniarray diodes with the similar pitch as the detector array for easy measurement of critical parameters such as diode I-V characteristics and detector quantum efficiency. Typical I-V curves show excellent R o A products and strong reverse breakdown characteristics. Detector quantum efficiency was measured to be in the 60-70% range without an antireflection coating.

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Since its initial synthesis and investigation more than 40 years ago, the HgCdTe alloy semiconductor system has evolved into one of the primary infrared detector materials for high-performance infrared focal-plane arrays (FPA) designed to operate in the 3-5 µm and 8-12 µm spectral ranges of importance for thermal imaging systems. Over the course of the past decade, significant advances have been made in the development of thin-film epitaxial growth techniques, such as molecular-beam epitaxy (MBE), which have enabled the synthesis of IR detector device structures with complex doping and composition profiles. The central role played by in situ sensors for monitoring and control of the MBE growth process are reviewed. The development of MBE HgCdTe growth technology is discussed in three particular device applications: avalanche photodiodes for 1.55 µm photodetection, megapixel FPAs on Si substrates, and multispectral IR detectors.