N-nH complexes in GaAs studied at the atomic scale by cross-sectional scanning tunneling microscopy

• Published in: arXiv.org 2020-07
• Main Authors: Tjeertes, D, Verstijnen, T J F, Gonzalo, A, Ulloa, J M, Sharma, M S, Felici, M, Polimeni, A, Biccari, F, Gurioli, M, Pettinari, G, C \c{S}ahin, Flatté, M E, Koenraad, P M
• Format: Article
• Language: English
• Subjects: Atomic properties; Cross-sections; Density functional theory; Hydrogen storage; Hydrogenation; Microscopy; Nitrogen; Quantum dots; Scanning tunneling microscopy
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.2007.11879

Hydrogenation of nitrogen (N) doped GaAs allows for reversible tuning of the bandgap and the creation of site controlled quantum dots through the manipulation of N-nH complexes, N-nH complexes, wherein a nitrogen atom is surrounded by n hydrogen (H) atoms. Here we employ cross-sectional scanning tunneling microscopy (X-STM) to study these complexes in the GaAs (110) surface at the atomic scale. In addition to that we performed density functional theory (DFT) calculations to determine the atomic properties of the N-nH complexes. We argue that at or near the (110) GaAs surface two H atoms from N-nH complexes dissociate as an H\(_2\) molecule. We observe multiple features related to the hydrogenation process, of which a subset is classified as N-1H complexes. These N-1H related features show an apparent reduction of the local density of states (LDOS), characteristic to N atoms in the GaAs (110) surface with an additional apparent localized enhancement of the LDOS located in one of three crystal directions. N-nH features can be manipulated with the STM tip. Showing in one case a switching behavior between two mirror-symmetric states and in another case a removal of the localized enhancement of the LDOS. The disappearance of the bright contrast is most likely a signature of the removal of an H atom from the N-nH complex.