Temperature and frequency dependence of flicker noise in degenerately doped 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-metal transition by doping with phosphorus and boron (∼10¹⁹ cm⁻³). In this range of doping the noise (as quantified by the Hooge's parameter) is much larger than that seen in lightly doped Si. The f and T dependence shows a 1/f component whose strength increases exponentially with T (with activation energy ≈0.1-0.2 eV) although the resistivity is almost flat in this temperature range. For a sample on the metallic side of the transition the behaviour of the conductance fluctuation is very similar to that of disordered metals with the spectral power, S_V(f)∝1/f^α with α≈1-1.2. This is proposed to arise from the movement of defect complex involving P and interstitials/vacancies following a broad activated kinetics. Interestingly in a heavily doped sample, lying on the insulating side (but close to the insulator-metal transition) the spectral 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 from recombination-generation type mechanisms.