Valence bands offset between depleted semiconductors measured by photoelectron spectroscopy

A modified method to measure the valence bands offset by photoelectron spectroscopy (PES) between low doped and depleted semiconductors have been used. The surface photovoltage (SPV) and the charging effects modify the PES spectra of depleted semiconductors. The valence bands offset at the heterojunction of depleted ZnSe film and doped GaAs substrate have been measured. These samples were prepared by the laser ablation technique. The shift of PES spectra of ZnSe by about 6 eV has been observed due to the charging and SPV effects. The charging and SPV effects on PES spectra, have been reduced to negligible values in the presence of excess plasma (due to absorption from a secondary white light source) density of the order of 1018 cm-3. The effect of the charging and SPV is very small on the value of the valence bands offset measured in the presence of the excess plasma. This method to measure the valence bands offset is useful for samples prepared in ex situ conditions and with film thickness of the order of 100 nm