PHOTOREFLECTANCE OF ALXGA1-XAS GAAS AND GAAS/GAAS INTERFACES AT HIGH LIGHT INTENSITIES/

Photoreflectance measurements of multilayered AlxGa1-xAs/GaAs semicond uctor structure in the regime of high modulating laser powers are repo rted. The main photoreflectance feature observed at low powers at abou t 1.4 eV is related to Franz-Keldysh oscillations caused by electric f ield at the AlxGa1-xAs/GaAs interface. The value of electric field ded uced from these oscillations is in agreement with that determined from calculation using the accepted value of the AlxGa1-xAs/GaAs band offs et and the doping level in the GaAs layer. On increasing the power of the modulating laser, the spectrum changes its character and after dec omposition reveals a feature at the energy corresponding to GaAs bandg ap. The intensity of this line increases with the modulating laser pow er, moreover the line is in phase with the Franz-Keldysh oscillations. These observations are consistent with the assignment of the line to the photoreflectance at the underlying GaAs buffer/GaAs substrate inte rface. This finding underlines the altered character of the photorefle ctance spectra at high light intensities, compared to the standard low intensity regime.