OBSERVATION OF THE PHASE INVERSION IN PHOTOREFLECTANCE SPECTRA FROM ZNSE GAAS(001) HETEROSTRUCTURES/

The pump photon energy dependence of photoreflectance (PR) of a ZnSe/G nAs heterostructure has been measured at 77 K. The phase inversion in the PR signal is observed for the pump photon energy when it decreases from above to below the excitonic absorption edge of ZnSe. The observ ation of the phase inversion in PR is explained in terms of the modula tion of the built-in electric field at the interface of the ZnSe/GaAs heterojunction, not at the ZnSe surface. It provides evidence of a bui lt-in triangular-well potential and of hole traps at the ZnSe/GaAs int erface. This argument is confirmed by photoreflectance excitation spec troscopy. (C) 1998 American Institute of Physics. [S0003-6951(98)03436 -6].