Submonolayer structure of an abrupt Al/GaAs{001}-(2×4) interface

Abstract

The structure of As-terminated Al/GaAs͕001͖-(2ϫ4) has been determined in atomic detail using angleresolved secondary-ion-mass spectrometry. We find an abrupt interface is formed at room temperature by deposition of 0.3 ML of Al onto GaAs͕001͖-(2ϫ4) prepared in situ by molecular-beam epitaxy. The Al atoms are found to adsorb in the troughs between two As 2 dimers, in ordered sites 0.79Ϯ0.10 Å above the surface plane. These dimers maintain their 2.73-Å spacing after Al deposition. The structure is determined from angular distributions of Al ϩ and Ga ϩ ions desorbed by keV ions and computer simulations of the ionbombardment event.

Collisions of ions with surfaces at chemically relevant energies: Instrumentation and phenomena

“…[27][28][29] The keV collision energy regime, with collision energies up to about 10 keV, has a long research history, dating back to the first ion scattering experiments. 2 Impact of keV ͑the SIMS experiment͒ 9,30,31 and MeV energy ͑plasma desorption͒ 32 ions causes ablation of target material and can be used for chemical analysis. These experiments can be performed in a quasi-nondestructive fashion with respect to molecules present at or near the surface.…”

Atomic placement of Al on the GaAs {001}c(4×4)reconstruction determined by angle-resolved secondary-ion mass spectrometry

“…The desorption mechanisms that lead to the formation of these peaks have been detailed in previous papers. 22,25,27 Briefly, the largest peaks arise by di-rect collision between fourth-layer As and third-layer Ga causing Ga ϩ ion ejection along the common bond direction. Features at higher polar angles arise from a mix of mechanisms related to the missing As atoms in the reconstructed surface.…”

“…It is known that slight variations in ͓As 4 ͔/͓Ga͔ flux ratio and sample temperature upon termination of growth lead to very different surface reconstructions. 22,25,27 To eliminate variations in the surface reconstruction a systematic process was developed to grow a reproducible c(4ϫ4) reconstruction. Our procedure was to terminate the Ga flux while the sample was at growth temperature, then reduce the As flux by a factor of 10 by lowering the As cell temperature while simultaneously reducing the sample temperature to 650 K. At this point the RHEED pattern indicates a c(4ϫ4) reconstruction.…”

“…Studies conducted on Ga-rich GaAs ͕001͖ surfaces show Al to react with GaAs disrupting the surface, while on As-rich surfaces there appears to be no interfacial disruption. 26,27 Upon initial deposition of Al ͓р1 monolayer ͑ML͔͒ onto As-rich surfaces, metal islands are observed to form in the dimer rows 28 followed by three-dimensional nucleation at approximately 3 ML of deposited Al. 26 As the deposition progresses, Al nucleation results in formation of ͑001͒ and mixed ͑001͒/͑011͒ crystallites.…”

In situ passivation of GaAs surface with aluminum oxide with MOVPE

“…Therefore, an Al 2 O 3 /GaAs stack without any interfacial layer can be obtained if proper Al layer is deposited on GaAs surface in an MOVPE reactor. Although the growth of Al/GaAs structure using molecular beam epitaxy (MBE) was reported [7], there is no report about Al/GaAs structure for Al 2 O 3 dielectric, using MOVPE. The formation of Al 2 O 3 dielectric by selective oxidation of AlAs was reported, such as in the fabrication of vertical cavity lasers [8][9][10].…”