UNPINNED BEHAVIOR OF THE ELECTRONIC-PROPERTIES OF A P-GAAS(CS,O) SURFACE AT ROOM-TEMPERATURE

The evolution of the surface band bending, photovoltage, and recombina tion rate is experimentally studied in situ by means of photoreflectan ce and photoluminescence techniques under deposition of cesium and oxy gen on the surface of epitaxial p- and n-type GaAs layers at room temp erature. The evolution of the band bending is explained in terms of Fe rmi level pinning by initial and adatom-induced donor-like and accepto r-like surface states. For the surface of p-type GaAs multiple reversi ble variations of the electronic properties are observed under alterna te Cs and O-2 deposition. This unpinned behavior proves that adatom-in duced surface states dominate over defect-induced states. Hysteresis i n the dependences of photovoltage and photoluminescence intensity on t he band bending shows that variations of the concentrations or cross s ections of surface capture and recombination centers take place at the first cycles of Cs and O-2 deposition.