Hole spin relaxation in intrinsic quantum wells

We observe a fast decay of the photoluminescence intensity in intrinsic quantum wells (QW), for excitation energies above the QW gap. This fast decay is interpreted as the result of the transfer of excitons from optically active states (angular momentum J = 1) to non-optically active ( J = 2) ones; the transfer is driven by the spin relaxation of holes. This observation leads us to propose a method to measure directly the hole spin relaxation time in intrinsic quantum wells, independently of any other spin-flip mechanism. We determine then the dependence of the hole spin relaxation time versus the photogeneration energy in various lattice matched {GaAs}/{AlGaAs} and strained {GaInAs}/{GaAs} QW. The obtained results are essential in order to interpret the spin relaxation mechanism of holes in intrinsic quantum wells.