Berlin 2024 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 21: Heterostructures, Interfaces and Surfaces I

HL 21.8: Talk

Tuesday, March 19, 2024, 11:30–11:45, EW 561

Chemical and energetical structure at P-rich InP(100)/TiO₂ heterointerface — •Agnieszka Paszuk¹, Jennifer Velázquez Rojas², Mohammad Amin Zare Pour¹, David Ostheimer¹, Christian Höhn², Roel van de Krol², and Thomas Hannappel¹ — ¹Fundamentals of Energy Materials, Technische Universität Ilmenau — ²Institute for Solar Fuels, Helmholtz-Zentrum Berlin für Materialien und Energie GmbH, Germany

In the photoelectrochemical cells with the highest solar-to-hydrogen conversion efficiencies, III−V photoabsorbers are integrated with a metal oxide passivation layer and a catalyst. Such devices require preparation of ideal (buried)interfaces to minimize the losses of the photogenerated charge carriers. Here, we study atomic layer deposition (ALD) of TiO₂ on phosphorus terminated (P-rich) InP(100) surfaces prepared in a metalorganic vapor phase epitaxy reactor. Samples were transferred in ultra-high vacuum to an ALD chamber. Titanium tetrachloride and water were used as the titanium and oxygen precursors, respectively. The preparation of P-rich InP(100) and the deposition of the TiO₂ were monitored in situ by ellipsometry and optical spectroscopy, respectively. After selected precursor pulses, the surface chemical composition and the electronic structure were determined by photoemission spectroscopy. We observed a nucleation delay of TiO₂ and during the first deposition cycles, a limited interaction of the water and the Ti precursor due to stable P-P bonds on the InP(100) surface. The TiO₂ layers show +4 oxidation state and we find no evidence of the presence of Ti³⁺ state, which might act as trap centres.

Keywords: metal oxide passivation layer; titanium dioxide; III-V semiconductors; photoelectrochemistry; X-ray photoelectron spectroscopy