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At least 55 records · Page 3

Evaluation of a 32 x 32 InSb CCD for use in astronomy

We have been fortunate to receive several infrared CCD array detectors on loan from Santa Barbara Research Center. The devices are evaluation samples, not commercially available at this time. Dr. Alan Hoffman of SBRC has made the arrangements for this loan and provided considerable technical support to this project. One aim of this project has been to evaluate the performance potential of this array technology, using astronomical objects. A quick summary of our findings is given. In short, we have found the imaging properties to be excellent under both low and high background conditions and the sensitivity to be quite good (each pixel is competitive with current InSb single-detector systems in use for astronomy). We anticipate improved low-background performance when we run these detectors at a lower and more stable temperature. The device characteristics are described, laboratory testing is summarized, and the first astronomical imaging is presented. Various circuits developed (clocks, clock drivers, DC supplies, clamp-amplifier, and a real time display system) are given.

Forrest, W. J.↗

Growth of semiconductor compound single crystal InSb by floating zone method (M-3)

Floating zone methods have potential applications in growing single high-quality semi-conductor crystals. In this method, melts can be sustained without containers and, therefore, are free from contamination from the containers. The main objective of this project is to use the Image Furnace to study a large diameter, (20 mm) single crystal of InSb under microgravity conditions. The behavior of the liquid column is recorded on the VTR tapes and is compared with what is expected theoretically. The single crystal grown in space is characterized by comparing it with single crystals grown on the ground with respect to crystallographic and electronic properties. The goal of this project is to confirm the effects of the microgravity on the single crystals.

Nakatani, I.↗

Laser damage tests on InSb photodiodes at 1.064 micron and 0.532 micron

InSb photodiodes were examined for performance degradation after pulsed laser illumination at 0.532 micron and 1.064 micron. Incident laser powers ranged from 6 x 10 exp-18 micron-watts to 16 micron-watts in a 50 pm diameter spot. Dark current and spectral response were both measured before and after illumination. Dark current measurements were taken with the diode blanked off and viewing only 77 K surfaces. Long term stability tests demonstrated that the blackbody did not exhibit long term drifts. Other tests showed that room temperature variations did not affect the diode signal chain or the digitization electronics used in data acquisition. Results of the experiment show that the diodes did not exhibit changes in dark current or spectral response performance as a result of the laser illumination. A typical change in diode spectral response (before/after laser exposure) was about 0.2 percent +/- 0.2 percent.

Bearman, G. H.↗

Influence of Contact Angle, Growth Angle and Melt Surface Tension on Detached Solidification of InSb

We extended the previous analysis of detached solidification of InSb based on the moving meniscus model. We found that for steady detached solidification to occur in a sealed ampoule in zero gravity, it is necessary for the growth angle to exceed a critical value, the contact angle for the melt on the ampoule wall to exceed a critical value, and the melt-gas surface tension to be below a critical value. These critical values would depend on the material properties and the growth parameters. For the conditions examined here, the sum of the growth angle and the contact angle must exceed approximately 130, which is significantly less than required if both ends of the ampoule are open.

Wang, Yazhen↗

Te-and Zn-Doped InSb Crystals Grown in Microgravity

In 2002, within the SUBSA (Solidification Using a Baffle in Sealed Ampoules) investigation, seven doped InSb crystals were grown in microgravity at the International Space Station. The key goals of the SUBSA investigation are: (a) to clarify the origin of the melt convection in space laboratories; (b) to reduce melt convection to the level which allows reproducible diffusion-controlled segregation; (e) to explore the submerged baffle process and liquid encapsulation in microgravity. 30 crystal growth experiments were conducted in the ground unit, to optimize the design of flight ampoules and to test the transparent SUBSA furnace developed by TecMasters Inc. The specially designed furnace, allowed observation of the crystal growth process (melting, seeding, motion of the solid-liquid interface, etc.). In the summer of 2002, eight crystal growth experiments were conducted in the Microgravity Science Glovebox (MSG) facility at the ISS. Four Te-doped (k = 0.5) and three Zn-doped (k2.9) crystals were grown on undoped seeds. In one experiment, we were not able to seed and grow. The seven grown crystals were sectioned and analyzed using SIMS. The design of the SUBSA ampoules, the segregation data and the video images obtained during the SUBSA flight experiments will be presented and discussed.

Ostrogorsky, A. G.↗

Initial Transient in Zn-doped InSb Grown in Microgravity

Three Zn-doped InSb crystals were directionally solidified under microgravity conditions at the International Space Station (ISS) Alpha. The distribution of the Zn was measured using SIMS. A short diffusion-controlled transient, typical for systems with k greater than 1 was demonstrated. Static pressure of approximately 4000 N/m2 was imposed on the melt, to prevent bubble formation and dewetting. Still, partial de-wetting has occurred in one experiment, and apparently has disturbed the diffusive transport of Zn in the melt.

Ostrogorsky, A G.↗

Growth of InSb and InI Crystals on Earth and in Microgravity

During the past 40 years, dozens of semiconductor crystal growth experiments have been conducted in space laboratories. The subsequent analysis of the space-grown crystals revealed (i) that weak convection existed in virtually all melt-growth experiments, (ii) de-wetting significantly reduced the level of stress-induced defects, and (iii) particularly encouraging results were obtained in vapor-growth experiments. In 2002, following a decade of ground based research in growing doped Ge and GaSb crystals, a series of crystal growth experiments was performed at the ISS, within the SUBSA (Solidification Using a Baffle in Sealed Ampoules) investigation. Te- and Zn-doped InSb crystals were grown from the melt. The specially designed furnace provided a side-view of the melt and precise seeding measurement of the growth rate. At present, under sponsorship of CASIS (Center for the Advancement of Science in Space, www.iss-casis.org), we are conducting ground-based experiments with indium mono-iodide (InI) in preparation for the "SUBSA II" ISS investigation, planned for 2017. The experiments include: i) Horizontal Bridgman (HB) growth and ii) Vapor Transport (VT) growth. Finite element modeling will also be conducted, to optimize the design of the flight ampoules, for vapor and melt growth.

Ostrogorsky, A. G.↗

A microwave-biased millimeter- and submillimeter-wave detector using InSb.

Description of a high-purity n-type indium antimonide sample mounted in a reentrant cavity, cooled to 4.2 K, and operated as a millimeter-wave detector. The scheme utilizes a down-conversion process, and free-carrier absorption is the mechanism responsible for the detection process. Power applied at the millimeter-wave frequency causes a change in the material conductivity, which in turn causes a change in the X-band power absorption. Cavity perturbation techniques are used to analyze the scheme. The detector was operated successfully at frequencies between 35 and 150 GHz with no long-wavelength or short-wavelength cutoff observed. The scheme offers a fast, highly sensitive, and rugged detector with low conversion loss.

Eldumiati, I. I.↗

Thermal conductivity of liquid InSb and liquid Ga.

The mean thermal conductivity of liquid gallium was measured as 70 (plus or minus 7) W/m/K over the range 250-550 C. For indium antimonide, Kl = 2.04Ks at the melting temperature with Kl = 9.23 W/m/K- as a reasonable absolute value.

Seidensticker, R. G.↗

Preparing InSb Substrates

Molecular-beam epitaxial substrates passivated by chloride film growth. Chloride layer produced by direct chlorination, by chloride radicals in solutions, or by formation of preliminary oxide layer followed by chloride substitution.

Vasquez, R. P.↗

Development of InSb and Si:Ga arrays for ISO camera

The Infrared Space Observatory (ISO) satellite will contain a 60 cm telescope. A 4 faces pyramid mirror feeds each experiment with a 3 arc minute part of the telescope field of view. The camera system is described. The arrays for the 3 to 5 and 5 to 17 micron channel are also discussed.

Sibille, F.↗

Epitaxial growth of InSb (111) on sapphire (0001)

Indium antimonide has been epitaxially grown directly on sapphire. Reflection high-energy electron diffraction, TEM, and SEM data are presented to show that the indium antimonide layer is epitaxial, has an abrupt interface with the sapphire, and grows in the 111-line direction. Mobility data show room-temperature mobilities as high as 10,000 sq cm/V s from some regions on the wafer.

Jamison, K. D.↗

Experience with the UKIRT InSb array camera

The cryogenic infrared camera, IRCAM, has been operating routinely on the 3.8 m UK Infrared Telescope on Mauna Kea, Hawaii for over two years. The camera, which uses a 62x58 element Indium Antimonide array from Santa Barbara Research Center, was designed and built at the Royal Observatory, Edinburgh which operates UKIRT on behalf of the UK Science and Engineering Research Council. Over the past two years at least 60% of the available time on UKIRT has been allocated for IRCAM observations. Described here are some of the properties of this instrument and its detector which influence astronomical performance. Observational techniques and the power of IR arrays with some recent astronomical results are discussed.

Mclean, Ian S.↗