Spontaneous Loss of Spin Coherence in GaAs/Si Heterostructure

We present a possible way to optically inject spins into silicon. In this work, GaAs and Silicon-on-Insulator (SOI) wafers are bonded together by an ultrathin Ag layer using UHV wafer bonding. Standard optical pump-probe Kerr microscopy technique is applied to examine the spin coherence in the GaAs/Si heterostructure. In some areas of the bonded wafer, a relatively long spin coherence time of T2*=0.5 ns is observed in the GaAs. In other parts of the sample, the spin coherence is observed to decay much more rapidly (T2*=140ps). One possible explanation is that the quality of the bond varies across the wafer and that the strongly bonded areas exhibit spin transport from GaAs to silicon.