INVESTIGATION OF THE ROLE OF ZNSE FILMS ON GAAS USING ACOUSTOELECTRICVOLTAGE SPECTROSCOPY

The electrical properties of the ZnSe/GaAs heterostructure have been i nvestigated using the acoustoelectric voltage spectroscopy technique, and in particular, the role of the high-resistivity ZnSe on the surfac e passivation of the GaAs substrate has been evaluated. From the trans verse acoustoelectric voltage (TAV) spectra, the carrier type and conc entration, energy band offsets, and the energy levels of various trap states at the heterostructure interface have been found. The effect of heterostructure epitaxial layer on the surface properties of GaAs has been studied by comparing the normalized changes in TAV amplitude for samples of various epitaxial layers and different thicknesses. From a ll these measurements, surface recombination velocities (S) have been evaluated. For the pseudomorphic ZnSe films (thickness less-than-or-eq ual-to 0.15 mum) on GaAs, a reduction in S has been found. As the thic kness of the ZnSe film was increased, the presence of a large number o f interface states due to the introduction of misfit dislocations was detected using TAV measurements.