Exciton Spin Relaxation Properties in Zero Dimensional Semiconductor Quantum Dots

Abstract

Exciton spin relaxation dynamics in zero dimensional semiconductor quantum dots is studied. Exciton spin relaxation behavior in disk-shaped InGaAs quantum dots is measured by monitoring the time-evolution of exciton luminescence with resolving polarization. The spin relaxation time is studied in terms of the lateral extent of the dot. The spin relaxation time is found to depend strongly on the lateral extent of the dot. The spin relaxation time in quantum dots extending 30–40 nm is as long as 1 ns at 4 K, which is almost twice as long as the recombination lifetime and considerably longer than that in quantum wells. The spin relaxation time decreases with rising temperature and it became longer in quantum dots with larger exciton energy level separation. These results suggest the importance of the exciton–acoustic phonon interaction on spin relaxation in a semiconductor quantum dot at low temperature.