Abstract
Ballistic electron emission microscopy (BEEM), a derivation of scanning tunnelling microscopy (STM), is a recently developed technique that is most often used to measure local potential barrier height variations in metal-semiconductor systems (i.e. Schottky barriers). Here, for the first time, the successful application to the study of buried lateral period superlattices, produced by molecular beam epitaxial growth on a vicinal GaAs(001) substrate, is reported. The structure consists of thin Au and GaAs films on top of the buried AlAs GaAs superlattice and finally a GaAs substrate. Simultaneously obtained STM topographical images of the Au film and BEEM images of the ballistic electrons reaching the GaAs substrate reveal the expected periodic modulation only in the BEEM image. In addition, spectroscopic examination of the potential barrier at various places over the samples reveals a bimodal distribution consistent with a modulation of Al x Ga 1− x As mole fraction perpendicular to the surface steps. More detailed analysis reveals a compositional modulation larger than previously detected in such samples.
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