Optical spin injection in CuGaSe2/GaAs films

We have investigated polarization-resolved photoluminescence in epitaxially grown CuGaSe2/GaAs(001) films. Spin-polarized excitons are optically excited both below and above the characteristic crystal field splitting of the chalcopyrite. At low temperatures, a large exciton spin polarization of 35% is measured under resonant pumping but this is reduced by an order of magnitude and reverses its sign for nonresonant excitation. The measurements suggest that optical pumping within a small energy window just above the band gap results in the preferential generation of light holes and electrons that exhibit a long spin relaxation time, comparable to the recombination time in CuGaSe2. (c) 2006 American Institute of Physics.