Solute trapping of group III, IV, and V elements in silicon by an aperiodic stepwise growth mechanism

Abstract

With rapid solidification following pulsed laser melting, we have measured the dependence on interface orientation of the amount of solute trapping of several group III, IV, and V elements (As, Ga, Ge, In, Sb, Sn) in Si. The aperiodic stepwise growth model of Goldman and Aziz accurately fits both the velocity and orientation dependence of solute trapping of all of these solutes except Ge. The success of the model implies a ledge structure for the crystal/melt interface and a step-flow mechanism for growth from the melt. In addition, we have observed an empirical inverse correlation between the two free parameters (-"diffusive speeds") in this model and the equilibrium solute partition coefficient of a system. This correlation may be used to estimate values of these free parameters for other systems in which solute trapping has not or cannot be measured. The possible microscopic origin of such a correlation is discussed.

Supersaturating silicon with transition metals by ion implantation and pulsed laser melting

“…11 Figure 3(a) shows XTEM images of the (001) and (111) samples implanted with Au and melted with the Nd:YAG laser. Whereas the (001) sample was found by XTEM to be single-crystalline and free of defects, stacking faults are clearly visible in the (111) sample.…”

“…To achieve supersaturation, the solidification speed v must be high enough, compared to the diffusive speed v D of the solute, for deviations from local interfacial equilibrium to cause significant solute trapping. [8][9][10][11] Ion implantation and PLM have been used to synthesize single-crystalline silicon supersaturated with a range of dopants from group III-group VI and their diffusive speeds have been well characterized. [10][11][12][13][14][15] Transition metals, however, have proven challenging; early attempts at non-equilibrium doping of Si with transition metals resulted in complete segregation out of the solid during resolidification.…”

“…[8][9][10][11] Ion implantation and PLM have been used to synthesize single-crystalline silicon supersaturated with a range of dopants from group III-group VI and their diffusive speeds have been well characterized. [10][11][12][13][14][15] Transition metals, however, have proven challenging; early attempts at non-equilibrium doping of Si with transition metals resulted in complete segregation out of the solid during resolidification. [16][17][18][19][20] There have been isolated reports of supersaturated concentrations of Au (Ref.…”

Synthesis of Ge1−xSnx alloys by ion implantation and pulsed laser melting: Towards a group IV direct bandgap material

“…In-situ time resolved reflectivity measurement indicated a melt duration of 53 À 66 ns, which was then used to estimate the solidification speed of about 7 À 10 m s À1 , according to numerical solutions of the heat equation. 28 Rutherford backscattering spectroscopy (RBS) with a 2 MeV He þ ion beam was used to determine the impurity concentration, the crystallinity, and the Sn substitutionality in the samples. Raman spectroscopy was used to study the crystallinity post-PLM, specifically to detect bonding arrangements such as the Sn-Sn, the Sn-Ge, and the Ge-Ge.…”

Comparison of structure and properties of femtosecond and nanosecond laser-structured silicon

“…The dopants are incorporated into the melt and rapid solidification that follows laser melting can produce highly supersaturated solid solutions. 13 Sulfur may be incorporated into the fs-formed structures by a similar process; the fs laser fluences used are not far above the ablation threshold, and so a molten layer forms at the surface after the laser-induced plasma recombines and the electrons and lattice equilibrate. 14 In summary, laser microstructuring of silicon surfaces in the presence of SF 6 with either ns or fs laser pulses produces strong below-band gap absorption and photocarrier generation.…”