Formation of cylindrical n/p junction diodes by arsenic enhanced diffusion along interfacial misfit dislocations in p-type epitaxial Si/Si(Ge)

Abstract

Arsenic enhanced diffusion along individual misfit dislocations in Si/Si(Ge) heterostructures has been detected and imaged using scanning electron microscopy (SEM) and in the electron beam induced current (EBIC) mode. The formation of buried cylindrical, or conical, diodes surrounding misfit dislocations has been observed. The diffusion enhancement is not uniform for each dislocation. EBIC/SEM micrographs reveal a dark recombination contrast in the vicinity of the dislocation core and a white generation signal within the space-charge region of the surrounding n/p diode. Based on an experimental isoconcentration etching profile and a simple model for enhanced diffusion, the dislocation diffusion coefficient for arsenic is estimated to be up to six orders of magnitude higher than that in the host crystal.

Checked patterned elemental distribution in AlGaAs nanowire branches via vapor–liquid–solid growth

“…[2][3][4] An important phenomenon that is observed often in ternary NWs is the non-uniform compositional distribution, which is sensitive to various NW structural features. That observation had been demonstrated earlier in thin films, where dislocations formed during growth can act as diffusion paths, a phenomenon known as pipe diffusion, 5,6 leading to elemental segregation along threading dislocations. Regarding NW structures, morphology, crystal defects and crystal phase can influence the local composition in various material systems.…”

High responsivity near-infrared photodetectors in evaporated Ge-on-Si

“…[7][8][9] This discrepancy can be associated to the modified diffusion dynamics of phosphorus in highly defected films: while P diffusion is well described in terms of a vacancy mechanism in homogeneous crystals, 10,11 threading and misfit dislocations largely enhance the diffusion velocity. 12,13 In our samples P diffusion mainly occurs along preferential paths determined by threading dislocations; hence, P easily penetrates down to the heterointerface where it accumulates as its further diffusion into the Si substrate is hampered by the limited temperature. Noteworthy, P accumulation takes place at the interface where the defect density is larger, i.e., it is quite effective in widening the depletion region on the Ge side of the junction.…”

Nanodot Formation in Thermally Annealed UHV-RTCVD Grown Si1-XGeX Epitaxial Layers on Silicon for Photovoltaics

“…Misfit dislocation induced strain fields developed in our SiGe film readily lead to the formation of dots on top of misfit dislocations during annealing. It is believed that the strain driven dot formation occurs locally via Ge pipe diffusion [19] along the misfit dislocation field, which results in concentration increase at intersections, where Gerich dots nucleate and grow. These strain relaxation mechanisms are responsible on nanodot formation at the dislocation crossings.…”