Regensburg 2007 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 46: Poster 2

HL 46.24: Poster

Donnerstag, 29. März 2007, 15:00–17:30, Poster A

Doping dependence of vacancy formation kinetics on III-V semiconductor surfaces — •Sebastian Landrock, Philipp Ebert, and Knut Urban — Institut für Festkörperforschung, Forschungszentrum Jülich, 52425 Jülich

We observed by variable-temperature STM the formation of anion and cation vacancies on GaAs and InP (110) surfaces. The formation rates of vacancies are classically described by a pre-exponential factor times the Boltzmann factor, containing the activation barrier and the temperature. The pre-exponential factor arises from vibrational excitations of the crystal lattice and is thus in the order of the Debye frequency, i.e. 10¹² to 10¹³ Hz. We found, however, striking deviations from this expectation as well as differences between n-type GaAs and p-type GaAs/InP: On p-type GaAs and InP (110) surfaces anion vacancies exhibit pre-exponential factors in the order of 0.001 to 10 Hz (and a barrier of 0.3 to 0.5 eV), while for n-type GaAs we found a pre-exponential factor roughly 10 to 15 orders of magnitudes larger for Ga vacancies. We show that the ultra-low pre-exponential factors on p-type material arise from a rate limiting process, which is a one dimensional adatom diffusion mediating the desorption of anions as di-atom molecules. In contrast, on n-type GaAs the Ga vacancies are formed by atomic desorption.