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Solid‐phase‐epitaxial growth and formation of metastable alloys in ion implanted silicon

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3 Author(s)
Narayan, J. ; Solid State Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830 ; Holland, O.W. ; Appleton, B.R.

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Transmission electron microscopy (cross‐section and plan‐view) and ion backscattering techniques have been combined to study the details of solid‐phase‐epitaxial (SPE) growth in Sb+, In+, Bi+, Ga+, and As+ implanted silicon after furnace annealing in the temperature range 450 to 650 °C. The ion implanted amorphous layer grew ‘‘defect‐free’’ in 〈001〉 orientations and the crystalline–amorphous (c–a) interface during growth contained undulations ∼5 Å over the intervals of 200–500 Å. During SPE growth in 〈111〉 orientations, the c–a interface was atomically smooth initially, but eventually became nonplanar due to the formation of twins. From SPE growth rates at different temperatures, the activation energy associated with the growth was determined to be 2.6±0.3 eV. The dopant concentrations in defect‐free SPE grown layers were found to exceed equilibrium solid solubility limits by as much as a factor of 560 in the Si–Bi system. The absolute maximum concentrations, corresponding to the intersections of free‐energy versus composition curves of amorphous and crystalline silicon, were calculated and the results were compared with the observed concentrations. The observed concentrations, which were found to depend upon the amorphous state or free energy of as‐implanted silicon, approached the calculated limits in the case of the Si–Sb and Si–As systems. However, for the Si–In, Si–Ga, and Si–Bi systems, interfacial segregation and solute redistribution during SPE growth prevented the maximum achievable concentrations. The concentrations of dopants in excess of the solubility limits could be precipitated out completely only after annealing treatments at relatively high temperature- - s (≥1050 °C).

Published in:

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures  (Volume:1 ,  Issue: 4 )