Determination of landau level lifetimes in n-GaAs

The lifetime of electrons in the first excited Landau level of n-GaAs is determined from a combination of measurements of far infrared cyclotron resonance induced absorption and conductivity change. Values of T₁ of the order of 10^?8s for densities of excited electrons of 10¹¹ cm^?3 and a temperature dependence of T^?2.7 are found. An upper limit for the N = 0 Landau level to donor recombination time of the order of 10^?9s was derived from pulsed conductivity measurements.