Impact of UV Nanosecond Laser Annealing on Composition and Strain of Undoped Si_0.8Ge_0.2 Epitaxial Layers

Abstract

Ultraviolet Nanosecond Laser Annealing (UV-NLA) was performed on 30 nm-thick Si 0.8 Ge 0.2 epitaxial layers. The various regimes encountered, depending on the melt depth after single pulse UV-NLA, are described and discussed in this paper. Energy densities around 2.00 J/cm 2 and above led to the formation of pseudomorphic layers with a strong Ge redistribution. Starting from uniform Si 0.8 Ge 0.2 layers, Ge segregation toward the surface resulted in the formation of a Ge-rich surface layer with up to 55 at.% Ge for 2.00 J/cm 2 . Such pseudomorphic SiGe layers with a graded composition and a Ge-rich surface may find promising applications such as contact resistance lowering in doped layers.

Investigation of recrystallization and stress relaxation in nanosecond laser annealed Si1−xGex/Si epilayers

“…For Si0.8Ge0.2 samples, (yellow circles in Figure 13a), it was found that, in the surface melt regime (at 1.55 and 1.59 J/cm²), laser annealing did not cause any relaxation, although the surface had locally started to melt (with a surface coverage lower than 20%, however). For higher energy densities, at the end of the surface melt regime (1.70 and 1.80 J/cm²), solidification started from a non-planar l/s interface [28], leading to the same results as those described in the previous section, i.e. the formation of defects in the whole regrown layer, accompanied by partial relaxation (~30% in this case).…”

“…"30 nm" and "Si0.7Ge0.3"). The Ge depth profiles are not shown here, as their shapes are very similar to the ones shown in Figure 2 (those associated with the 30nm thick Si0.8Ge0.2 and Si0.6Ge0.4 samples were reported in previous papers [28,39]. For energy densities corresponding to the early stages of the surface melt regime (i.e.…”

“…Ong et al succeeded in having layers with a Ge concentration at 36 at.% which remained perfectly strained. In addition, our previous results on Si0.8Ge0.2 [28] showed that these layers could be partially relaxed or remained strained depending on the laser annealing regime (submelt, partial or full melt).…”

“…Hence, it can be safely concluded that the nanostructures detected by AFM are those observed by TEM and that they are due to the same phenomenon: the progressive melting and covering of the surface by isolated melted islands. Complementary SP2 Haze analysis (not shown) was performed to track the evolution of the surface quality with the energy density, as already done for Si0.8Ge0.2 in a previous work [28]. It was shown that the surface quality was degraded in the surface melt regime (increase of the Haze signal).…”

Non-isothermal phase-field modelling with thermocapillary convection: Laser-written in-plane SiGe heterostructures for photonic applications

“…Another alternative is the application of non-conventional thermal sources, like lasers, to post-process semiconductor alloy thin films grown on substrates with high thermal conductivities. 24,25 Such methods allow for achieving extremely high temperature gradients (10 9 K m -1 ) and cooling rates (10 5 K s -1 ), which are required to ensure the stability of the solid/liquid interface. Recently, by using laser processing of amorphous SiGe thin films deposited on silicon substrates, the fabrication of non-dendritic SiGe microstripes was demonstrated with steady-state compositional profiles that can be tuned by applying different constant scan speeds in the range of 0.1-100 mm s -1 .…”