Hopping conduction in partially compensated doped silicon

We have measured the dc electrical resistance of partially compensated (5--50 %) ion-implanted Si:P,B (both n and p type), over the temperature range 0.05--30 K. The temperature behavior is consistent with the prediction of the model for variable-range hopping (VRH) with a Coulomb gap {ρ}(T)=ρ₀exp(T₀/T)1/2 over a temperature range 6.5T₀/T24. We observe deviations from this behavior at our high- and low-temperature extremes. In the low-temperature region, the resistivities show a stronger temperature dependence than the Coulomb-gap model prediction. The high-temperature deviation appears consistent with a transition from Coulomb-gap VRH to Mott VRH.