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

TL;DR

This study uses cross-sectional scanning tunneling microscopy and density functional theory to investigate N-nH complexes in GaAs at the atomic level, revealing hydrogen dissociation behavior and manipulability of these complexes.

Contribution

It provides atomic-scale insights into N-nH complexes in GaAs and demonstrates their manipulation using STM, combining experimental imaging with theoretical calculations.

Findings

H atoms from N-nH complexes dissociate as H₂ molecules near the surface

N-1H complexes show reduced local density of states (LDOS)

N-nH complexes can be manipulated and switched using STM tip

Abstract

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.