Thermally-Stimulated Current Investigation of Dopant-Related D− and A+ Trap Centers in Germanium for Cryogenic Detector Applications
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- Domange, J., Olivieri, E., Fourches, N. et al. J Low Temp Phys (2012) 167: 1131. doi:10.1007/s10909-012-0547-1
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Thermally-stimulated current measurements provide a sensitive tool to characterize carrier traps in germanium detectors for direct dark matter search. Using this technique at cryogenic temperatures, very shallow traps have been detected with binding energies of a fraction of a meV, associated with the dopant species in the D−(A+) charge states. A positive identification of these traps is achieved through an analysis of the field dependence of the carrier emission rates, which demonstrates a potential well for the trapped carriers in the form of a polarization well in r−4, consistent with Lax’s model for carrier trapping by a neutral center. The density of these traps is assessed, and implications for the space-charge cancellation procedure in cryogenic Ge detectors are discussed.