High-quality large-area MBE HgCdTe/Si

Abstract

HgCdTe offers significant advantages over other similar semiconductors, which has made it the most widely utilized variable-gap material in infrared (IR) focal plane array (FPA) technology. HgCdTe hybrid FPAs consisting of two-dimensional detector arrays that are hybridized to Si readout circuits (ROIC) are the dominant technology for second-generation infrared systems. However, one of the main limitations of the HgCdTe materials system has been the size of lattice-matched bulk CdZnTe substrates, used for epitaxially grown HgCdTe, which have been limited to 30 cm 2 in production. This size limitation does not adequately support the increasing demand for larger FPA formats which now require sizes up to 2048 3 2048, and only a single die can be printed per wafer. Heteroepitaxial Si-based substrates offer a cost-effective technology that can be scaled to large wafer sizes and further offer a thermalexpansion-matched hybrid structure that is suitable for large format FPAs. This paper presents data on molecular-beam epitaxy (MBE)-grown HgCdTe/Si wafers with much improved materials characteristics than previously reported. We will present data on 4-and 6-in diameter HgCdTe both with extremely uniform composition and extremely low defects. Large-diameter HgCdTe/Si with nearly perfect compositional uniformity and ultra low defect density is essential for meeting the demanding specifications of large format FPAs.

Infrared Detectors for the Future

“…With the cost of 6 inch Si substrates being ≈ $100 vs. $10 000 for the 7 × 7 cm 2 CdZnTe, significant advantages of HgCdTe/Si are evident [24]. Despite the large lattice mismatch (≈ 19%) between CdTe and Si, MBE has been successfully used for the heteroepitaxial growth of CdTe on Si.…”

Fast Detection of Precipitates and Oxides on CdZnTe Surfaces by Spectroscopic Ellipsometry

“…From a chemical standpoint, one expects that Cd oxidizes mainly as Cd(OH) 2 and CdO, and Te as TeO 2 . 20 Both the e(x) of CdO 21 and that of TeO 2 [22][23][24] have an indirect absorption edge within the measured range.…”

“…The drive towards large-area substrates for the production of mercury-cadmium telluride (Hg 1-x Cd x Te) infrared detectors 1 has produced two viable (and apparently equivalent) solutions for the midwavelength atmospheric window (3-5 lm): cadmium telluride (CdTe) on Si, [2][3][4] and CdTe on Ge. 5 However, neither of these solutions yields the anticipated results in the long-wavelength detection range (from 8 to 12 lm), for which bulk, latticematched cadmium-zinc telluride (Cd 1-y Zn y Te) is still indispensable.…”

Fabrication and Characterization of Small Unit-Cell Molecular Beam Epitaxy Grown HgCdTe-on-Si Mid-Wavelength Infrared Detectors

“…diameter Si, Ge and GaAs substrate materials using molecular beam epitaxy (MBE) and metal organic vapor phase epitaxy (MOVPE) techniques have been demonstrated as alternatives to the technical challenges and high cost associated with the use of large CdZnTe substrates in combination with MBE or liquid phase epitaxy (LPE) material growth for large format HgCdTe FPAs. [4][5][6][7][8][9] The use of 4-in. and 6-in.…”

“…MWIR HgCdTe/Si growth has been demonstrated, and single color HgCdTe/Si LWIR 256 · 256 pixel 30 lm unit-cell FPAs show the potential for extending HgCdTe/Si technology to LWIR wavelengths. 6,8,9 Sofradir and LETI recently provided the first demonstration of large format MWIR 640 · 512 and 1280 · 1024 pixel 15 lm unit-cell FPAs on MBE grown 4-in. HgCdTe/Ge wafers, thus showing MBE HgCdTe growth on alternative substrates to CdZnTe as a viable approach to yield high quality large format, small pixel FPAs.…”