Increased dephasing length in heavily doped GaAs

Ion implantation of S and Te followed by sub-second flash lamp annealing with peak temperature about 1100 oC is employed to obtain metallic n++-GaAs layers. The electron concentration in annealed GaAs is as high as 5×1019 cm-3, which is several times higher than the doping level achievable by alternative methods. We found that heavily doped n++-GaAs exhibits positive magnetoconductance in the temperature range of 3-80 K, which is attributed to the magnetic field suppressed weak localization. By fitting the magnetoconductance results with Hikami-Larkin-Nagaoka model, it is found that the phase coherence length increases with increasing carrier concentration at low temperature and is as large as 540 nm at 3 K. The temperature dependence of the phase coherence length follows〖 l〗_∅∝T^η (η~0.3), indicating defect-related scattering as the dominant dephasing mechanism. In addition, the high doping level in n-type GaAs provides the possibility to use GaAs as a plasmonic material for chemical sensors operating in the infrared range.