Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures

In situ photoreflectance study of the effects of sputter/annealing on the Fermi level at (001)n- and p-type GaAs surfaces

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We report a photoreflectance study of the effects of Ar<sup>+</sup> sputtering and thermal annealing on the Fermi level (V<inf>F</inf>) on (001) n- and p-type GaAs with large, uniform electric fields. The measurements were performed in situ in an ultrahigh vacuum (UHV) chamber. The effect of the sputtering was to move V<inf>F</inf> from midgap to near the conduction band for both types of material. Subsequent UHV annealing (350°C) and air exposure restored V<inf>F</inf> its original midgap value. The implication of these observations for various models of Schottky barrier formation will be discussed. Our work also demonstrates the need to simultaneously measure both n- and p-type material in order to obtain unambiguous results.