Temperature and doping dependence of electron spin relaxation in GaSb

Electron spin relaxation times in n-doped as well as in nominally undoped bulk GaSb are measured with time-resolved circular dichroism and Faraday rotation induced by 1.55 νm, 150 fs pulses. Degenerately n-doped samples are characterized by ultrashort relaxation times of ∼2 ps. In contrast, we find much larger time constants and a strong temperature dependence of the spin relaxation time in moderately n-doped and undoped GaSb. The longest spin relaxation time is found to be ∼30 ps for an undoped sample at temperatures below T = 50 K. Many aspects of the results can be attributed to the large spin-orbit coupling in GaSb, consistent with the D'yakonov-Perel' theory of spin relaxation. In addition, magneto-optical measurements reveal an effective electronic Landé factor of |g*| = 9 ± 1.