UNPINNED BEHAVIOR OF THE FERMI-LEVEL AND PHOTOVOLTAGE ON P-(100)GAAS SURFACE FACILITATED BY DEPOSITION OF CESIUM

The preparation technique of (100)GaAs surface with unpinned electroni c properties is further developed in this work. It was proved that the unpinned behavior of the Fermi level and surface photovoltage on p-(1 00)GaAs surface was facilitated by the deposition of cesium. The surfa ce preparation technique included removal of oxides in the solution of HCl in isopropanol and transfer to a UHV set-up in nitrogen atmospher e. The variations of band bending and surface photovoltage were measur ed by means of photoreflectance spectroscopy after anneals at successi vely increasing temperatures, Without Cs deposition the band bending v aried only by 50-100 meV as the annealing temperature increased from 3 00 to 600 degrees C. Deposition of a monolayer of Cs, followed by anne aling at 400 degrees C, caused a pronounced decrease of band bending. The evolution of surface photovoltage, which depends both on band bend ing and on the rates of capture and recombination of the photogenerate d carriers on the surface, was more diverse and sensitive to the detai ls of surface treatment. Possible mechanisms of cesium influence on th e electronic properties of the surface are discussed.