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 ha s been studied by laser reflectometry using two wavelengths. At 1.32 m u m, GaAs and GaAlAs are totally transparent for our growth temperatur e (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 wavel ength for the control of Bragg mirror, with layer thickness in the ran ge 60 to 90 nm. Effective optical indices have been determined for bot h wavelengths by comparing in-situ and ex-situ measurements. By 1.32 m u m reflectivity, in-situ determination of the composition of GaAlAs t hick layer as well as the period of a GaAs/GaAlAs multi quantum well ( MQW) have been determined. Finally, by 0.514 nm reflectivity, Bragg re flectors centred at 980 nm have been grown. X-ray diffraction and refl ectivity measurements performed on the reflectors confirm at 1% reprod ucibility and accuracy of the stop band centre wavelength.