Hole polarization and slow hole-spin relaxation in ann-doped quantum-well structure

We present a study of the dependence of the hole-spin relaxation on the electron density in an n-modulation-doped 75-{} GaAs/Alₓ{Ga}_{1{{-}}x}$As quantum well by using cw and time-resolved photoluminescence techniques, at low temperature. The electron concentration has been continuously varied from ${10}¹¹$ to ${10}¹²$ ${cm}^{{{-}}2}$. A slow hole-spin relaxation time has been found ({}1 ns). A polarization decrease has also been observed when the in-plane wave vector of the photocreated holes increases. Calculations are presented which qualitatively support the latter experimental findings.