Raman scattering observations andab initiomodels of dicarbon complexes in AlAs

Surface morphology of heavily carbon-doped GaAs grown by solid source molecular beam epitaxy

“…This leads to reduction in arrival rate of Ga atoms at the step edges. The dicarbon defects may also reduce the number of suitable sites at the step edges for Ga atoms to bond, due to them having fewer unsaturated bonds compared to As atoms [13]. Hence, short migration length of Ga and C atoms, coupled with fewer unsaturated bonding sites at the step edges will impede the movement of steps and fulfill the requirements for step bunching described in Frank's impurity mechanism reported by Kandel et al [11].…”

Density-functional calculations of carbon diffusion in GaAs

“…A second carbon atom encountering this defect is then conveniently placed to form the (C-C) i dicarbon interstitial complex found previously. 15 This is composed of one gallium and two carbon atoms sharing a Ga lattice site, with the carbon pair strongly bound together, but perturbed by the presence of the neighboring gallium atom. A more likely encounter, at least in the early stages of annealing, would be with a C As atom, in which case a (C-C) As dicarbon complex would form.…”

“…12 Ramanscattering observations supported by ab initio theoretical modeling have shown that new dicarbon defects consisting of a pair of carbon atoms lying at an arsenic lattice site, (C-C) As ϩ , or interstitial dicarbon defects, (C-C) i 2ϩ , are formed when annealing heavily doped material. [13][14][15] These defects are deep donors, or double donors, respectively, hence three or four holes are lost for each dicarbon complex formed ͑provided that all C atoms were active as acceptors intitially͒. Their formation implies the activation energy for carbon diffusion has a relatively low value in material where ͓C͔տ5ϫ10 19 cm Ϫ3 .…”

Density-functional calculations of carbon doping in III-V compound semiconductors

“…Dicarbon defects, (C-C) P , similar to those observed in AlAs and GaAs, may also be responsible. [5][6][7] These are deep donors, and we understand there is spectroscopic evidence for them. 8 An interpretation of this unusual behavior could be that the creation of C P acceptors is always accompanied by the formation of a greater or equal number of donors, in a similar manner to the codoping technique, which enhances electrical activity of one type by the deliberate addition of the other type for reasons which are not understood.…”