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approvedosi15_supplie.pdf2015-03-27 18:39:14Oliver Supplie


Author: Oliver Supplie
Requested Type: Oral
Submitted: 2015-03-13 10:03:48

Co-authors: M.M. May, S. Brückner, P. Kleinschmidt, T. Hannappel

Contact Info:
TU Ilmenau, Institute of Physics, PV Group
Gustav-Kirchhoff-Str. 5
Ilmenau,   98693

Abstract Text:
Pseudomorphic GaP/Si(100) quasisubstrates are promising for metamorphic III-V/Si photovoltaic tandem cells and lattice-matched GaPN-based photochemical tandem diodes for high-efficient solar watersplitting [1]. Preparation of the GaP/Si(100) interface, however, impacts subsequent heteroepitaxy and is not understood at the atomic scale. Analyzing reflection anisotropy spectroscopy (RAS) signals of single-domain surface dimers (free of antiphase disorder) in combination with DFT calculations, we found indirect indications for a kinetically limited formation of abrupt Si-P interfaces [2]. Here, we study the GaP nucleation itself time-resolved with in situ RAS, which reveals that a dielectric anisotropy is formed at the heterointerface during the first alternating P and Ga precursor pulses and remains during further GaP layer growth [3]. X-ray photoelectron spectroscopy (XPS) indicates the existence of Si-P bonds [3]. Furthermore, XPS and RAS reveal that sub-monolayer coverages of (Ga,P) residuals from previous processes can lead to an inverted sublattice orientation of the GaP epilayer, which agrees with a change to Si-Ga interfacial bonds as predicted by DFT depending on the chemical potential during nucleation.
[1] S. Hu et al., EES 6:2984 (2013); O. Supplie et al., JAP 115:113509 (2014).
[2] O. Supplie et al., PRB 90:235301 (2014).
[3] O. Supplie et al., JPC Lett. 6:464 (2015).