Scaling analysis of the low temperature conductivity in neutron‐transmutation‐doped 70Ge:Ga

Abstract

AbstractWe report on the scaling analysis of low temperature electron transport properties of nominally uncompensated neutron‐transmutation‐doped 70Ge:Ga samples in the critical regime for the metal‐insulator transition. Ga concentration (N) and temperature (T) dependent conductivities σ(N, T) are shown to collapse onto a single universal curve using finite temperature scaling of a form σ(N, T) ∝ Tx f(|N/Nc — 1|/Ty) with x ≈︂ 0.38 and y ≈︂ 0.32 for the very small region of N = Nc ± 0.004Nc. The conductivity critical exponent μ = x/y = 1.2 ± 0.2 found from this analysis is significantly larger than μ ≈︂ 0.5 found from the analysis we performed previously on the same series of samples covering the much larger region of the concentration Nc < N < 1.4Nc. Determination of the true critical region, either N = Nc ± 0.4% or N = Nc ± 40%, is necessary in the future for the reliable determination of μ in Ge:Ga.