Phase transformations in ion-mixed metastable (GaSb)1−x(Ge2)x semiconducting alloys

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Abstract
Low energy (75–175 eV) Ar+ ion bombardment during film deposition has been used to produce well‐mixed amorphous GaSb/Ge mixtures which, when annealed, transform first to single phase polycrystalline metastable (GaSb)1−x(Ge2)x alloys before eventually transforming to the equilibrium two‐phase state. At 500 °C, for example, the annealing time ta required for the amorphous to crystalline metastable (ACM) transformation was ∼10 min, while ta for the crystalline metastable to equilibrium (CME) transformation was >6 h. The exothermic enthalpy of crystallization and the onset temperature of the ACM transition were determined as a function of alloy composition using differential thermal analysis. The thermodynamic data was then used to calculate the surface energy per unit area σ of the amorphous/metastable‐crystal interface. σ was found to exhibit a minimum between x=0.3 and 0.4. The driving energy for the transition from the crystalline metastable state to the equilibrium two‐phase state was of the order of 0.12 kJ cm−3 while the activation barrier was ∼19 kJ cm−3. Thus, the metastable alloys, which had average grain sizes of 100–200 nm and a lattice constant which varied linearly with x, exhibited good thermal and temporal stability.