The ZnSe/GaAs heterojunctions formed by epitaxially grown ZnSe thin fi
lms on S-treated GaAs substrates are characterized by the photovoltaic
measurements. By analyzing the photovoltaic spectra obtained at diffe
rent temperatures, the broad-band photovoltaic signal is assigned to t
he cross-band photon-absorption transitions between the valence band o
f GaAs and the conduction band of ZnSe near the heterointerface. The b
and alignment of the ZnSe/S-GaAs heterojunction is determined to be of
a type-II configuration with a conduction-band offset of 168 meV at r
oom temperature.