Dresden 2003 – scientific programme

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HL: Halbleiterphysik

HL 47: Pr
äparation/Charakterisierung

HL 47.1: Talk

Thursday, March 27, 2003, 15:00–15:15, BEY/154

Potential and dopant mapping at p-n junctions using scanning tunneling microscopy — •Nikos D Jäger¹, M Marso², K Urban¹, E R Weber³, and Ph Ebert¹ — ¹Inst. f. Festkörperforschung, Forschungszentrum Jülich, 52425 Jülich — ²Inst. f. Schichten und Grenzflächen, Forschungszentrum Jülich GmbH, 52425 Jülich — ³Dept. of Materials Science, University of California, and Materials Science Division, Lawrence Berkeley Laboratory, Berkeley, CA 94720, U.S.A.

We use cross-sectional scanning tunneling microscopy to map out the potential distribution at GaAs p-n junctions with sub-nanometer resolution and correlate the potential distribution to the simultaneously obtained dopant distribution. We explain the imaging mechanism to be founded on an interplay of the build-in potential of the p-n junction and the tip-induced band bending. This allows us to determine the metallurgical interface and the width of the depletion zone, as well as an atomically resolved electronic interface identification, and to demonstrate local fluctuations in the dopant atom distribution beyond statistical expectations. We show that the electronic p-n interface exhibits a much larger roughness than the underlying essentially atomically sharp metallurgical interface. It arises from the individual electrostatic screening fields around each dopant atom near the interface and from a clustering of dopant atoms. The clustering is ascribed to many body effects in the screened Coulomb interactions of the charged dopant atoms during growth. Furthermore local scanning tunneling spectroscopy unveils variations in electronic characteristics of local dopant atom distribution fluctuations, that can be explained by confining potential barriers.