Optical monitoring of the growth rate reduction by CCl4 during metalorganic vapour-phase epitaxy deposition of carbon doped GaAs

Metalorganic vapor-phase epitaxy (MOVPE) growth of heavily doped GaAs has been studied by reflectometry with a 632.8 nm laser beam. The measurement of reflection intensity gives the growth rate and the morphology of the layer. Small changes in the refractive index due to high carbon doping (10(20) cm(-3) and above) gives rise to oscillations in the reflectometric signal. A reduction in the growth rate of C-doped GaAs, was attributed to the etching by GaClx (x = 1-3) species associated with the use of CCl4. There is no significant change in the growth rate if the growth temperature is ;smaller than a critical value depending on [Ga(CH3)(3)]/[CCl4] ratio. However, above this critical temperature, a steep decrease in the growth rate and a poor morphology of the surface layer are observed and lead to the reduction in reflection intensities. These results are analyzed using microscopic observations and a thermodynamic calculation. (C) 1998 Elsevier Science B.V. All rights reserved.