The evolution of Ga and As core levels in the formation of Fe∕GaAs (001): A high resolution soft x-ray photoelectron spectroscopic study

Abstract

A high resolution soft x-ray photoelectron spectroscopic study of Ga and As 3d core levels has been conducted for Fe/GaAs (001) as a function of Fe thickness.This work has provided unambiguous evidence of substrate disrupting chemical reactions induced by the Fe overlayer -a quantitative analysis of the acquired spectra indicates significantly differing behaviour of Ga and As during Fe growth, and our * Corresponding author, e-mail: t.shen@salford.ac.uk 2 observations have been compared with existing theoretical models. Our results demonstrate that the outdiffusing Ga and As remain largely confined to the interface region, forming a thin intermixed layer. Whereas at low coverages Fe has little influence on the underlying GaAs substrate, the onset of substrate disruption when the Fe thickness reaches 3.5 Å results in major changes in the energy distribution curves (EDCs) of both As and Ga 3d cores. Our quantitative analysis suggests the presence of two new As environments of metallic character; one bound to the interfacial region and another which, as confirmed by in-situ oxidation experiments, surface segregates and persists over a wide range of overlayer thickness. Analysis of the corresponding Ga 3d EDCs found not two, but three new environments -also metallic in nature.

Stress and interdiffusion during molecular beam epitaxy of Fe on As-rich GaAs(001)

“…A net tensile strain remains, even when the voids are refilled by Fe because of the smaller volume of Fe compared with As or Ga. The substitution of bcc Fe atoms by As and Ga, on the other hand, leads to compressive strain because the volume of Fe-As and Fe-Ga species of the alloy precipitates reported previously [23][24][25][26]30], e.g. Fe 2 As, FeAs, FeAs 2 [33], or Fe 2+x Ga 1−x [34], is even larger by several per cent than that of Fe-Fe units [33,34].…”

“…Concerning deposition at elevated temperatures, Schönherr et al [16] recommend an optimum growth temperature of 50 • C at which very smooth Fe layers are obtained on As-rich substrates as confirmed by Z-contrast scanning transmission electron microscopy (STEM) [27,28]. On Ga-rich substrates, on the other hand, considerable interdiffusion takes place even during Fe deposition at room temperature, generating subsequent intermixed layers of Fe-As, Fe-Ga-As and Fe-Ga at the Fe/GaAs interface [29,30]. Ga-rich surfaces are typically obtained after decapping of As-protected GaAs(001) buffer layers prepared by III/V-facilities.…”

Atom-to-atom interactions for atomic layer deposition of trimethylaluminum on Ga-rich GaAs(001)-4 × 6 and As-rich GaAs(001)-2 × 4 surfaces: a synchrotron radiation photoemission study

“…For multi-element (In)GaAs, a common method of surface pretreatment prior to in-vacuum annealing is As capping [4] by thermal annealing in As 2 flux [5], followed by a chemical rinse [6]. Subsequent in-vacuum annealing of these samples removes the more volatile As and produces an oxygen-free surface, but one that does not have the desired surface Ga/As ratio.…”

“…Subsequent in-vacuum annealing of these samples removes the more volatile As and produces an oxygen-free surface, but one that does not have the desired surface Ga/As ratio. It turns out to be low, say 0.73 [4], compared with an untreated sample, say 1.26 (not shown). The process has clearly changed the surface stoichiometry as well as the surface reconstruction.…”

Surface and interface analysis of electrochemically synthesized ferromagnetic/semiconducting Ni/GaAs(001) thin film

“…using photoemission found the formation of NiAs and the segregation of Ga, possibly diluted in Ni. On the other hand, for Fe/GaAs, considerable inter‐diffusion takes place during the Fe deposition at room temperature, resulting in intermixed layers of Fe–As, Fe–Ga–As and Fe–Ga at the interface . Introducing an Au capping or hard metallic layer of Ti between the FM/semiconductor layer generally avoids the intermixing and inter‐diffusion of substrate materials up to a certain level; however, the magnetic properties of the FM film degrade.…”