Photoluminescence studies of epitaxial Si 1- xGe x and Si 1- x-yGe xC y layers on Si formed by ion beam synthesis

Low temperature (2 K) photoluminescence (PL) properties of epitaxial Si _{1- x}Ge _x and Si _{1- x-y}Ge _xC _y layers on Si ( x = 0.13 and y = 0.014 at peak concentration) formed by ion beam synthesis (IBS) have been investigated. Samples were prepared by a high-dose Ge with/without C ion implantation (I ²) at room temperature and by subsequent three different crystallization techniques: (i) furnace annealing (FA) process up to 840°C, (ii) ion beam-induced epitaxial crystallization (IBIEC) process with 400 keV Ge or Ar ions at 300-350°C, and (iii) IBIEC process followed by FA process up to 640°C (IBIEC + FA). Although FA-grown Si _{1- x-y}Ge _xC _y samples showed G-line (C _sSi _iC _s complex) emission at 0.969 eV, IBIEC-grown samples presented a sharp I ₁ non-phonon emission at 1.0193 eV. This indicates that C atoms agglomeration is dominant for FA-grown samples, while a creation of trigonal tetravacancy cluster is dominant for IBIEC-grown samples. On the other hand, (IBIEC with Ge ions + FA)-grown Si _{1- x-y}Ge _xC _y samples showed neither G-line nor I ₁-related emissions, which indicates that good crystalline Si _{1- x-y}Ge _xC _y layers without C agglomeration were formed by this process. In contrast, (IBIEC with Ar ions + FA)-grown samples exhibited novel successive PL vibronic sidebands at 0.98-1.03 eV. From their excitation power dependence measurements, they were found to be associated with exciton bound to defects levels created by Ar ⁺ bombardment.