Regensburg 2025 – scientific programme

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O: Fachverband Oberflächenphysik

O 65: Solid-Liquid Interfaces: Reactions and Electrochemistry III

O 65.6: Talk

Wednesday, March 19, 2025, 16:15–16:30, H6

TiO2 passivation of GaInP(100) surfaces — •David Ostheimer¹, Julius Kühne^2,3, Sahar Shekarabi¹, Agnieszka Paszuk¹, Mohammad Amin Zare Pour¹, Ian D. Sharp^2,3, Wolfram Jägermann⁴, and Thomas Hannappel¹ — ¹TU Ilmenau, Inst. of Physics, Fundamentals of Energy Materials, Ilmenau, Germany — ²TU Munich, Walter Schottky Institute, Garching, Germany — ³TU Munich, Physics Department, TUM School of Nat. Sciences, Garching, Germany — ⁴TU Darmstadt, Surface Science Lab, Darmstadt, Germany

GaInP is widely used in III-V-based photoelectrochemical devices as a top photoabsorber or charge-selective contact, achieving high solar-to-fuel conversion efficiencies. To enhance stability under HER conditions, a thin TiO2 protection layer can be applied. This study investigates the electronic structure of the TiO2/GaInP(100) interface. TiO2 was deposited via atomic layer deposition (ALD) on p-type GaInP(100) grown on GaAs(100) substrates. Two surfaces were prepared: a phosphorus-rich (P-rich) (2x1)-like surface transferred contamination-free under ultra-high vacuum (UHV) and a naturally oxidized surface. X-ray and UV photoelectron spectroscopy revealed a slightly thinner interfacial oxide in the UHV-transferred sample. Initial ALD cycles formed an oxide nearly stoichiometric to the native oxide, but both samples exhibited strong Fermi level pinning, resulting in similar band alignments. These findings highlight the influence of initial oxides on interface control in III-V semiconductors.

Keywords: III-V semiconductors; TiO2; Electronic structure