Effects of disorder on electron spin dynamics in a semiconductor quantum well

Using the spin of the electron to carry information, instead of or in addition to its charge, could provide advances in the capabilities of microelectronics. Successful implementation of spin-based electronics requires preservation of the electron spin coherence. In n-doped semiconductors, long spin-coherence times have been observed, with a maximum at a ‘magic’ electron density. Here, we vary the density in a two-dimensional electron gas, and show that spin coherence is lost because of the interplay between localization by disorder and dynamical scattering. By measuring the electron Landé g -factor dependence on density, we determine the density of states (DOS), which characterizes the disorder potential. Using our knowledge of the DOS, a simple model estimates the temperature and excitation intensity dependence of the g factor, qualitatively agreeing with experiments. This agreement confirms the importance of disorder and provides predictive power for designing spin-based electronic devices.