IN-SITU CONTROL OF THE GROWTH OF GAAS GAALAS STRUCTURES IN A METALORGANIC VAPOR-PHASE EPITAXY REACTOR BY LASER REFLECTOMETRY

Metalorganic vapour phase epitaxy (MOVPE) growth of GaAs and GaAlAs has been studied by laser reflectometry using two wavelengths. At 1.32 mu m, GaAs and GaAlAs are totally transparent for our growth temperature (750 degrees C) so that layers up to a few micrometres thick can be monitored. On the other hand, 0.514 mu m proves to be an optimum wavelength for the control of Bragg mirror, with layer thickness in the range 60 to 90 nm. Effective optical indices have been determined for both wavelengths by comparing in-situ and ex-situ measurements. By 1.32 mu m reflectivity, in-situ determination of the composition of GaAlAs thick layer as well as the period of a GaAs/GaAlAs multi quantum well (MQW) have been determined. Finally, by 0.514 nm reflectivity, Bragg reflectors centred at 980 nm have been grown. X-ray diffraction and reflectivity measurements performed on the reflectors confirm at 1% reproducibility and accuracy of the stop band centre wavelength.