DEPENDENCE OF THE LINEAR AND QUADRATIC ELECTROOPTICAL COEFFICIENTS ONTHE QUANTUM-WELL THICKNESS

In this paper we report on electroreflectance measurements carried out in several (001) oriented GaAs/Al0.3Ga0.7As quantum wells. Using pola rized light we were able to separate both the linear (L(lambda), Pocke ls effect) and the quadratic (Q(lambda), Kerr effect) contributions to the electroreflectance spectra. We have found that the first one can be described by an intensity modulation mechanism, whereas the second one is well described by an energy modulation mechanism. L(lambda) is different from zero only in the spectral range of the light-hole trans ition, while in Q(lambda) both the heavy-hole and the light-hole trans itions contribute. We have also studied the dependence of the intensit y ratio between L(lambda) and Q(lambda) on the well thickness.