Thermodynamic analysis of growth rate reduction by VCl4 during metalorganic vapor-phase epitaxy of GaAs

The growth rate reduction of metalorganic vapor-phase epitaxy (MOVPE) vanad ium-doped GaAs layer by vanadium tetrachloride (VCl4) was studied. Laser re flectometry was used to monitor this reduction as a function of the VCl4 fl ow rate and substrate temperature. A growth rate reduction up to 60% has be en observed. The growth rate reduction follows a sublinear variation with t he flow rate of VCl4 and exhibits Arrhenius temperature dependence with an activation energy of 1.3 eV. Thermodynamic calculations, based on the minim ization of the Gibbs energy, have been performed on input system containing arsine, trimethylgallium, hydrogen and vanadium tetrachloride. It is found that the growth rate reduction is essentially due to the GaCl formation in gas and/or solid phase. The thermodynamics equilibrium results are very cl ose to those obtained experimentally. (C) 1999 Elsevier Science B.V. All ri ghts reserved.