Thermodynamic properties of AsH3 and its subhydrides

  • A. S. Jordan
  • A. RobertsonJr
Paper

Abstract

The thermodynamic properties of AsH3 and its subhydrides AsH and AsH2 have been evaluated from critically assessed or estimated spectroscopic data. The calculation of thermodynamic functions (free-energy function, entropy, enthalpy, and heat capacity) is based on statistical thermodynamics. For the first time, for all three species a complete set of these functions has been generated between 0 and 1600 K in tabular form. A combination of the free-energy functions with the standard enthalpies of formation of hydrides (derived from the photoionization mass-spectrometric bond energy values of Berkowitz) permits the determination of the gas phase composition in the pyrolysis of AsH3 during the MOMBE (CBE), HS-MBE, or MOCVD growth of III–V epitaxial layers that include As. Using a free-energy minimization technique, the equilibrium concentrations of AsH, AsH2, AsH3, As, As2, As4, H and H2 have been obtained at 1.013, 3.039 × 103 and 1.013 × 105 Pa (1 atm) in the temperature range between 800 and 1500 K. In the case of MOMBE, under equilibrium conditions in the hydrate cracker, the removal of carbon-containing radicals or oxygen is facilitated by atomic H and AsH with partial pressures of ~3.33 × 10−4 and 1.87 × 10−5 Pa, respectively, at 1300 K. In contrast, in low pressure MOCVD the species AsH and AsH2 are equally prominent, while in atmospheric pressure MOCVD the dominant subhydride is AsH2.

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Copyright information

© Chapman & Hall 1993

Authors and Affiliations

  • A. S. Jordan
    • 1
  • A. RobertsonJr
    • 2
  1. 1.AT&T Bell LaboratoriesMurray HillUSA
  2. 2.Engineering Research CenterPrincetonUSA

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