Experimental determination of valence band discontinuities at Cu(Al,Ga)(S,Se)2/GaAs(001) heterointerfaces using ultraviolet photoemission spectroscopy

Ultraviolet photoemission spectroscopy measurement was carried out for o(001) plane Cu(Al,Ga)(S,Se)(2) chalcopyrite structure epi layers grown on GaAs(001) substrates to determine valence band discontinuities, DeltaE(v), at the heterointerfaces. The values of DeltaE(v) were estimated to be about 1.2 eV for CuAlS2/GaAs. 1.0 eV for CuAlSe2/GaAs, 1.1 eV for CuGaS2/GaAs and 0.3 eV for CuGaSe2/GaAs. From these values and bandgap energies of the corresponding compounds, Cu(AI,Ga)(S,Se)2 System is considered to offer the TYPE-I heterostructures between the corresponding narrow bandgap materials and wide bandgap ones.