  We have demonstrated by electroluminescence the injection of spin polarized
electrons through Co/Al2O3/GaAs tunnel barrier into p-doped InAs/GaAs quantum
dots embedded in a PIN GaAs light emitting diode. The spin relaxation processes
in the p-doped quantum dots are characterized independently by optical
measurements (time and polarization resolved photoluminescence). The measured
electroluminescence circular polarization is about 15 % at low temperature in a
2T magnetic field, leading to an estimation of the electrical spin injection
yield of 35%. Moreover, this electroluminescence circular polarization is
stable up to 70 K.
