Pyrolysis Studies and Deposition of Sb Films Using the Novel Omvpe Source (i-Pr) 2 SbH
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PYROLYSIS STUDIES AND DEPOSITION OF Sb FILMS USING THE NOVEL OMVPE SOURCE (i-Pr) 2 SbH ROBERT W. GEDRIDGE, JR.,* KENNETH E. LEE, CHARLOTTE K. LOWE-MA Chemistry Division, Research Department, Naval Air Warfare Center Weapons Division, China Lake, CA 93555
ABSTRACT The novel antimony source compound di-isopropylantimony hydride, (i-Pr)2 SbH, was synthesized and evaluated for use as a volatile Sb-source compound for low temperature growth of Sb-containing semiconductor materials. (i-Pr)2 SbH was pyrolyzed in a horizontal atmospheric pressure organometallic vapor phase epitaxy (OMVPE) reactor using Ar and H2 as carrier gases. The gaseous exhaust products were analyzed by a residual gas analyzer. Complete pyrolysis of (i-Pr)2 SbH in our OMVPE reactor occurs around 300 'C and 350 IC in Ar and H 2 , respectively. A comparison between the pyrolysis temperatures and pyrolysis byproducts with respect to a proposed decomposition mechanism of (i-Pr) 2 SbH is presented. Sb films were grown on Si(100) and Si( 111) as low as 200 'C. The Sb films were analyzed by Auger and X-ray diffraction. These polycrystalline Sb films were free of detectable carbon by AES. X-ray diffraction data indicated that these Sb films were highly oriented in the [O0OL] direction.
INTRODUCTION Antimony-containing semiconductor materials are of interest for lasers, high speed electronic devices, and infrared detectors. InSb focal plane arrays are currently being used at observatories 1 all over the world for infrared astronomical imaging. InAsl-xSbx, which has the smallest band gap (x = 0.6, Eg = 0.1 eV at 300 K) of any of the Ill/V semiconductor materials, is of interest for infrared detection in the 8-12 lim spectral range. The cutoff wavelength at 77 K for InAsl-xSbx (x = 0.6) is = 9gm, although further reduction of the band gap is desired to extend the cutoff wavelength. The band gap can be reduced if the crystal lattice is dilated with the heavier Group V 3 3 2 element Bi. InAsl-xSb,, lnAsl_x~ySbyBix ,4 and InSbl.xBix have been grown by OMVPE using trimethylantimony (TMSb) as the Sb-source compound. However, in order to minimize the tendency of the Bi to phase separate and to limit the diffusion in these Bi alloys, low film growth temperatures are required. Bi concentrations as high as 6 atom % have been achieved when the OMVPE growth temperature was reduced to 275 1C.5 At this temperature TMSb is inefficiently pyrolyzed. Thus new Sb-source compounds are needed for lowering the OMVPE film-growth temperature and altering the chemistry to minimize unintentional impurity incorporation. 7 8 6 Alternative Sb precursors such as trivinylantimony triisopropylantimony, triallylantimony, 9 and tertiarybutylantimony have been evaluated for low temperature OMVPE film growth. To date, only triisopropylantimony has been successfully used to grow lnSb as low as 300 'C, the lowest reported InSb film growth temperature using a stable OMVPE Sb-source compound. However, the low vapor pressure (0.4 torr at 25 VC) of triisopropylantimony and its inefficient pyrolysis a
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