Charging and spin-polarization effects in InAs quantum dots under bipolar carrier injection

Carrier dynamics in quantum dot p-i-n diodes are studied using an ultrafast polarization-resolved pump-probe technique. It is demonstrated that for bipolar electrical injection there is a high probability of the independent capture of electrons or holes into the dots, resulting in dot charging. Voltage control of the charged exciton population, created via a combination of electrical and optical excitation, which exhibits a long lived spin polarization (or spin memory) is demonstrated.