Photovoltaic study of ZnSe/GaAs heterostructures

The ZnSe/GaAs heterojunctions formed by epitaxially grown ZnSe thin films on $S$-treated GaAs substrates are characterized by the photovoltaic measurements. By analyzing the photovoltaic spectra obtained at different temperatures, the broad-band photovoltaic signal is assigned to the cross-band photon-absorption transitions between the valence band of GaAs and the conduction band of ZnSe near the heterointerface. The band alignment of the $\mathrm{ZnSe}/S-\mathrm{GaAs}$ heterojunction is determined to be of a type-II configuration with a conduction-band offset of 168 meV at room temperature.