Temperature and frequency dependence of flicker noise in degeneratelydoped Si single crystals

Abstract

We report measurements of low-frequency (10-2 Hz<f<20 Hz)conductance fluctuations (flicker noise) over a temperature range 150 K<T<450 K in single crystalline Si across the insulator-metaltransition by doping with phosphorus and boron (~1019 cm-3). In this range of doping the noise (as quantified by the Hooge'sparameter) is much larger than that seen in lightly doped Si. The f and Tdependence shows a 1/f component whose strength increases exponentially withT (with activation energy ≈0.1-0.2 eV) although the resistivityis almost flat in this temperature range. For a sample on the metallic side ofthe transition the behaviour of the conductance fluctuation is very similar tothat of disordered metals with the spectral power, SV(f)∝1/fα with α≈1-1.2. This is proposed to arise from themovement of defect complex involving P and interstitials/vacancies following abroad activated kinetics. Interestingly in a heavily doped sample, lying onthe insulating side (but close to the insulator-metal transition) thespectral power contains discrete Lorentzians in addition to the 1/f term.The corner frequencies have an activated behaviour with activation energy≈0.45-1 eV. This behaviour, most likely, originates fromrecombination-generation type mechanisms.