Electrical characterization of As doped SiGe layers by laser annealing. The sheet resistances vs laser energy density (a) below 0.4 J/cm2 and (b) above 0.4 J/cm2, are presented in linear scale. Different annealing processes, as discussed in the following, are indicated.
(a) Sheet dopant concentration vs. laser energy density. The values of dopant activation degree, defined as the ratio of sheet carrier concentration and implanted dose, are given for every energy density. Dashed lines indicate the different energy density regions, previously given in Fig. 1 . (b) Carrier concentration profile measured by ECV for a sample treated with 1.18 J/cm2. A homogenous 1.15 × 1019 cm−3 n-type doping was measured far below the depth of the original SiGe layer. The SiGe layer thickness is now of about 90 nm and followed by a p-type substrate with doping concentration of about 1 × 1019 cm−3.
SIMS profile showing (a) Ge and (b) As-distributions in the SiGe layer after ELA at energy densities below 0.6 J/cm2. The Ge profiles are plotted in linear scale and arbitrary shifted vertically for a better comparison.
XTEM images of the SiGe layers after ELA at (a) 0.25 J/cm2 (b) 0.6 J/cm2, and (c) 0.85 J/cm2. For 0.25 J/cm2 defect formation, e.g., As clustering, in the fully crystallized As implanted region are visible. For 0.6 J/cm2 the contrast changes with the depth in the SiGe layer in agreement with the SIMS profile; (the inset plot represents the Ge atomic distribution as in Fig. 3(a) ). The regrowth yields single crystalline material without no visible dislocations or interface defects.
(a) Ge and (b) As SIMS profile of the SiGe layer after ELA at energy densities of 0.7, 0.9, and 1.35 J/cm2 which exceed the melting threshold at the SiGe/Si interface.
RBS/C spectra of As implanted SiGe showing the spectra for (a) 0.50 and 0.70 J/cm2 and (b) 1.18 J/cm2. Channeling spectra after laser annealing with different energy densities are presented in comparison with the channeling spectrum of an as-implanted sample.
Raman spectra of As implanted SiGe layers after laser annealing at laser energy densities of 0.25 J/cm2 (empty squares), 0.70 J/cm2 (empty circles) and 1.18 J/cm2 (stars). In the inset, the complete Raman spectra for laser energy densities of 0.25 and 0.70 J/cm2 are shown. The region of interest is presented in the left main plot for a better visibility of the Si-Si modes contribution from the SiGe layers and their corresponding Lorentz fits. The right plot shows exemplary the double Lorentz deconvolution. The deconvoluted thin full/thick dashed lines correspond to Si-Si modes from SiGe and Si, respectively. The SiGe Raman peaks shift indicates changes in strain or alloy composition of the layer. 18
Modeling results of the sample temperature distribution at laser energy densities of (a) 0.3 J/cm2, (b) 0.8 J/cm2 and (c) 1 J/cm2. A 7 nm a-SiGe/13 nm c-SiGe/ c-Si structure was considered and the melting temperature at different interfaces is marked. (d) Maximum melting depth for every layer function of energy density.
Total dopant (As + B) concentration and dopant activation in percent versus laser annealing density. The various scenarios of dopant contribution and SiGe layer formation processes are indicated.
Sheet concentration and dopant activation degree for B and As dopants using different annealing conditions.
Article metrics loading...
Full text loading...