Heteroepitaxy of HgCdTe (211)B on Ge substrates by molecular beam epitaxy for infrared detectors

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The Leti-Lir has studied II-VI compounds for infrared (IR) detection for more than 20 years. The need to reduce the production cost of IR focal plane arrays (FPAs) sparked the development of heteroepitaxy on large-area substrates. Germanium has been chosen as the heterosubstrate for the third generation of IR detectors. First, we report on the progress achieved in HgCdTe growth on 3-in. and 4-in. (211)B CdTe/Ge. Then, we discuss the choice of a new machine for larger size and better homogeneity. Finally, we present the latest results on third-generation IR multicolor and megapixel devices. First-time results regarding a middle wavelength infrared (MWIR) dual-band FPA, with a reduced pitch of 25 mm, and a MWIR 1,280 3 1,024 FPA will be shown. Both detectors are based on molecular beam epitaxy (MBE)-grown HgCdTe on Ge. The results shown validate the choice of Ge as the substrate for third-generation detectors.

Section: Mbe Growth Conditionsmentioning

confidence: 99%

Molecular beam epitaxy growth of HgCdTe on Ge for third-generation infrared detectors

Zanatta

Badano

Ballet

et al. 2006

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“…Two bumps per pixel devices can also be fabricated, as mentioned in other papers. 5,6 The dual-band detector consists of two back-to-back n-on-p photodiodes, obtained by growing a four-layer heterostructure. The x Cd = 0.3 layer allows detection of the 5-mwavelength radiation, while the x Cd = 0.4 allows detection of the 3-m-wavelength radiation.…”

Section: Device Structurementioning

confidence: 99%

“…Results obtained with these devices demonstrate good process eproducibility, because they are similar to those obtained on single-color detectors. 5,6 The diode spatial responses are obtained by scanning the device surface with a diffraction spotlight. These measurements show FWHM of 46 m for the 3-m cut-off diode and 35 m for the 5-m cut-off diode, which reflects the mesa proportions in a 50-m pixel pitch.…”

Section: Electro-optical Performancesmentioning

confidence: 99%

Recent developments of high-complexity HgCdTe focal plane arrays at leti infrared laboratory

Destéfanis

Astier

Baylet

et al. 2003

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INTRODUCTIONThe second generation of infrared detectors based on HgCdTe is today a mature technology used in production in several companies in the world. In France, Sofradir, which industrializes HgCdTe IRCMOS infrared detectors, uses a technology transferred by CEA/LETI/Infrared Laboratory several years ago.This technology is based 11 on the very simple approach of planar n-on-p ion-implanted photodiodes. HgCdTe is grown by liquid-phase epitaxy (LPE) on the Te-rich corner by the slider technique. Detector array interconnection to silicon readout integrated circuit (ROIC) is made by hot welding with indium bumps.From that time, this technology was continuously improved by LETI and Sofradir teams. Research conducted at LETI in collaboration with Sofradir in the last few years has led to new achievements. This includes improvements of the standard technology and development of new advanced technologies.For the standard technology, progress in the field of crystal growth was obtained increasing the size and the quality of CdZnTe (4-in. ingots) and HgCdTe LPE (20 cm 2 ) crystals. In the field of detector technology, reduction of the detector pitch (20 m) allowed array size increase (up to 640 × 512). Most of these improvements are already available at Sofradir.New advanced technologies undertaken at the Infrared Laboratory have led to feasibility demonstrations of advanced focal plane arrays. Some of them are presented in this paper. MEDIUM-WAVELENGTH INFRARED MULTICOLOR IRCMOS FOCAL PLANE ARRAYSIn the last few years, the interest in dual-band HgCdTe infrared photo-detectors has widely grown. A wide range of civilian (earth observation, meteorology) and military (target discrimination, background clutter rejection) applications exists for this type of component. For these reasons, a lot of work has beenIn this article, we present recent developments of the research in France at LETI infrared laboratory in the field of complex third-generation HgCdTe IRC-MOS focal plane arrays (FPAs). We illustrate this with three prototypes of FPAs made at LETI, which have involved some technological improvements from the standard process today in production at Sofradir. We present, using molecularbeam epitaxy (MBE) growth, a 128 × 128 dual-band infrared (photodetector)-complementary metal oxide semiconductor (IRCMOS) with a pitch of 50 m operating within 2-5 m. Using the more conventional liquid-phase epitaxy (LPE) growth, we show a new generation of high-performance long linear arrays (1500 × 2; pitch, 30 m) operating in medium-wavelength infrared (MWIR) or long-wavelength infrared (LWIR) bands based on a modular architecture of butted HgCdTe detection circuit and SiCMOS multiplexers. Finally, we present for the first time a megapixel (1000 × 1000) FPA with a pitch of 15 m operating in the MWIR band that exhibits a very high performance and pixel operability.

“…The surface film left over by the bromine (Br) and methanol (MeOH) etch was evaporated in situ at 250°C, as is routinely done [5][6][7] prior to HgCdTe growth. The evaporation is confirmed by the changes in the reflection high-energy diffraction and ellipsometric spectra.…”

Section: Methodsmentioning

confidence: 99%

“…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. 6 The preparation of this substrate material and its subsequent characterization are vital to ensure the quality of the epitaxial layers and for a variety of device fabrication steps.…”

Section: Introductionmentioning

confidence: 99%

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

Badano

Million

Canava

et al. 2007

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We study the surface chemistry of Cd 0.96 Zn 0.04 Te(211)B by X-ray photoelectron spectroscopy and ellipsometry. We obtain first the dielectric functions of amorphous Te and Cd on Cd 0.96 Zn 0.04 Te(211)B by in situ ellipsometry after growing thin films of each material by molecular beam epitaxy. We then study their oxidation in air and show that Cd oxidizes primarily as a hydroxide whereas Te is present as TeO 2 . In neither case is the oxidation of the films complete, as a substantial amount of either metallic Te or Cd remains even after several days of oxidation. We subsequently exploit an electroless chemical etchant based on Ce 4+ to produce Te-rich Cd 0.96 Zn 0.04 Te(211)B surfaces which oxidize very little in air. Another etchant containing KCN reduces the amount of a-Te substantially. Finally, we construct a tentative optical model for the Cd 0.96 Zn 0.04 Te(211)B surface that yields the abundance of amorphous Te on the surface.