Electron spin relaxation in bulk GaAs for doping densities close to the metal-to-insulator transition

TL;DR

This study investigates how electron spin relaxation in n-doped GaAs varies with temperature and doping levels near the metal-insulator transition, revealing a crossover in relaxation times.

Contribution

It provides experimental measurements of spin relaxation and noise power across doping levels and temperatures, highlighting the transition from localized to free electrons.

Findings

Longest spin relaxation time at low temperatures near the transition

Crossover in relaxation rates at 70 K between samples

Higher doping leads to longer relaxation times above 70 K

Abstract

We have measured the electron spin relaxation rate and the integrated spin noise power in n-doped GaAs for temperatures between 4 K and 80 K and for doping concentrations ranging from 2.7 x 10^{-15} cm^{-3} to 8.8 x 10^{-16} cm^{-3} using spin noise spectroscopy. The temperature dependent measurements show a clear transition from localized to free electrons for the lower doped samples and confirm mainly free electrons at all temperatures for the highest doped sample. While the sample at the metal-insulator-transition shows the longest spin relaxation time at low temperatures, a clear crossing of the spin relaxation rates is observed at 70 K and the highest doped sample reveals the longest spin relaxation time above 70 K.