Structural and electrical properties of In-implanted Ge

Abstract

We report on the effects of dopant concentration on the structural and electrical properties of In-implanted Ge. For In concentrations of 0.2 at. %, extended x-ray absorption fine structure and x-ray absorption near-edge structure measurements demonstrate that all In atoms occupy a substitutional lattice site while metallic In precipitates are apparent in transmission electron micrographs for In concentrations !0.6 at. %. Evidence of the formation of In-vacancy complexes deduced from extended x-ray absorption fine structure measurements is complimented by density functional theory simulations. Hall effect measurements of the conductivity, carrier density, and carrier mobility are then correlated with the substitutional In fraction. V

Electrical and structural properties of In-implanted Si1−xGex alloys

“…15 More details of the implantation process are given in a previous report. 9 The In concentrations (0.02-1.2 at. %) were determined with Rutherford Backscattering Spectrometry after annealing.…”

“…We used thin layers to enable the subsequent removal of the Si substrate for superior synchrotron-based measurements. 9 The influence of misfit dislocations near the thin layer/Si substrate interface was minimized by confining the implanted In depth distributions to at least 0.5 lm above the interface. Implantations were performed at 250 C to avoid amorphization, and the surface normal was offset 7 from the incident ion direction to avoid channeling.…”

“…6 In Ge substrates, device electrical performance can be significantly advanced, 7 with superior carrier mobility, 8 a higher In solidsolubility limit (>0.02 at. %), 9 and a shallower In acceptor level (0.0112 eV above the valence band). 10 Relative to Si, the narrow bandgap of Ge can, however, yield higher off-state leakage due to band-to-band tunneling (BTBT).…”

“…For In-doped Si and Ge, earlier work has shown that In atoms were electrically active and located on substitutional lattice sites when the In concentration was below the solidsolubility limits. 2,4 The formation of electrically inactive In metal precipitates 1,5,9 and In-V pairs 9,13,14 (where V denotes a vacancy) was observed when these thresholds were exceeded. While the electrical and structural properties of In-doped Si and Ge have been studied, those of In-doped Si 1Àx Ge x have yet to be reported.…”

Enhanced Electrical Activation in In-Implanted Si0.35Ge0.65 by C Co-Doping

“…We used a SiGe/Si heterostructure to enable the subsequent removal of the Si substrate for superior synchrotronbased measurements. [36] The influence of misfit dislocations near the SiGe/Si interface (due to the lattice mismatch between SiGe and Si) was minimized by confining the implanted C and In depth distributions to < 2 μm. Implantations were performed at 250°C to avoid amorphization and the surface normal was offset 7°from the incident ion direction to avoid channeling.…”