Berlin 2012 – wissenschaftliches Programm

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SYSD: Symposium SKM Dissertationspreis

SYSD 1: SKM Dissertation Prize

SYSD 1.3: Hauptvortrag

Montag, 26. März 2012, 12:40–13:00, EW 201

Si(100) in hydrogen ambient - new physics of an old suspect — •Henning Döscher — Helmholtz-Zentrum Berlin für Materialien und Energie, Germany — Technische Universität Ilmenau, Germany

III-V heteroepitaxy on Si(100) substrates is strongly desired for micro- and optoelectronics, in particular for terrestrial concentrator photovoltaics. One major challenge is preparing single-domain Si(100) surfaces to prevent the formation of anti-phase disorder during III-V nucleation. Numerous theoretical and experimental studies explore the generation of energetically favorable B-type double-layer steps in ultra-high vacuum (UHV). Atomic hydrogen exposure suppresses their formation, but optoelectronics are usually manufactured by (metalorganic) vapor phase epitaxy (VPE) in hydrogen ambient.

We investigate VPE processing of Si(100) by optical in situ spectroscopy and surface science techniques accessible by contamination-free sample transfer to UHV. Cooling under hydrogen flow went along with strong interaction between process gas and Si(100) surface, formation of a monohydride termination, and a rate-dependent imbalance of the (2x1)/(1x2) reconstruction domains. High pressure and slow cooling promotes dimer rows parallel to the step edges equivalent to a preference for A-type double layer steps thought to be energetically unfavorable. We explain the anomalous Si(100) step structure by a kinetic model based on vacancy generation, diffusion, and annihilation as evidenced by vacancy island nucleation and monolayer oscillations in our in situ signals. Anti-phase disorder-free GaP films grown on single-domain Si(100) serve as template for device integration.