Fundamental reactions controlling anion exchange during mixed anion heterojunction formation: Chemistry of As-for-Sb and Sb-for-As exchange reactions

Abstract

As-for-Sb and Sb-for-As anion exchange reactions have been investigated by the exposure of GaSb surfaces to As2 and As4 species and by the exposure of GaAs to Sb2, respectively. The effect of surface temperature, anion soak time, and anion species (either As2 or As4) on the chemistry governing the anion exchange reactions during GaAsySb1−y∕GaSb and GaSbyAs1−y∕GaAs heterostructure formation by molecular beam epitaxy is examined. It is found that when GaSb surfaces are exposed to arsenic, the anion exchange reaction competes with the formation of isoelectronic compounds, AsSby, which form clusters precipitating in the GaAsySb1−y∕GaSb heterostructures. The relative amount of GaAs and AsSby depends on the surface temperature, the As soak time, and on the As species, i.e., As2 or As4. We observe specific process conditions that minimize AsSby formation, yielding more abrupt heterojunction interfaces. In the case of the Sb2∕GaAs system, the Sb-for-As anion exchange does not occur to a significant degree, but surface segregation of antimony is found. A chemical model for the As-for-Sb anion exchange reaction is proposed.

Enhanced Crystal Quality of AlxIn1-xAsySb1-y for Terahertz Quantum Cascade Lasers

“…Only at a T g of 410 • C can lattice matching with InAs achieved. An explanation for this behavior may be found in the As-for-Sb exchange reaction found for other mixed group V materials like GaAsSb [14]. Due to its negative enthalpy, this reaction is favored with respect to the reverse reaction and its rate rises with T g for experiments using As 2 , which is in agreement with our observations.…”

Epitaxial growth and formation of interfacial misfit array for tensile GaAs on GaSb

“…7,8 The Sb atoms, however, do not react with the GaAs substrate to displace the As atoms. 9 Strain relief is achieved by a skipped Sb-Ga bond every 13 atomic sites which form the IMF array. 10 The tensile IMF has a similar atomic structure initiated by a single layer of As ͑001͒ atoms bonded to the underlying Ga ͑001͒ atomic layer.…”

Incorporation of Sb and As in MBE grown GaAsxSb1−x layers

“…16 According to this mechanism, the Sb mole fraction increases with the growth rate since the time an Sb site is exposed to As flux decreases, and hence, the rate at which this event takes place is reduced. The As-for-Sb exchange reaction was previously studied by Losurdo and co-workers 21 by exposing steady GaAs and GaSb surfaces to Sb and As fluxes, respectively. The authors found a transformation of the GaSb into GaAs while the reverse reaction is not found and conclude that the As for Sb exchange is favored due to the difference in the enthalpy of formation of the two reactions, 2GaSb + As 2 → 2GaAs + Sb 2 , ∆H • = −47.6 kJ mol −1…”