Picosecond surface restricted transient grating studies of carrier reaction dynamics at n-GaAs(100) interfaces

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Abstract
The surface restricted transient grating technique has been found to be sensitive to the Fermi level pinning surface states at the atomic interface of the native oxide layer of (100) GaAs. The sensitivity to these states is better than 10−4 of a monolayer. The grating signal associated with the surface states is eliminated by photoinduced removal of the oxide layer and hole transfer to Se−2 ions adsorbed to the surface. These results support the assignment of the signal to electronic factors associated with surface state species. The use of space charge field focusing of hole carriers to the surface has enabled a discrimination of the hole carrier reaction dynamics from those of the electron at the surface. In situ studies of interfacial hole transfer to Se−2 ions present at liquid junctions found the hole transfer time to be less than 30 ps. The selective quenching of the hole carrier through interfacial charge transfer has found that the hole carrier contributes to the optical dispersion in the 1 μ region to approximately the same extent as the electron.