Domination of adatom-induced over defect-induced surface states onp-type GaAs(Cs,O) at room temperature

The unpinned behavior of the Fermi level, photovoltage, and recombination velocity is demonstrated experimentally at room temperature for a p-type GaAs(Cs,O) interface by means of photoreflectance and photoluminescence techniques. This behavior manifests itself as the multiple reversible switching of surface band bending, the amplitude of photoreflectance, and photoluminescence intensity under alternate deposition of cesium and oxygen on a clean surface of epitaxial p-type GaAs layers. The results prove that cesium-induced donorlike surface states dominate over defect-induced states.