Figure 3: Carrier and spin injection from GaAs to TI.
(a) PTE current 
in the S1 sample, generated intentionally under an imbalanced excitation condition. The current rise observed when the photon energy is tuned above the bandgap energy of GaAs (
), with the onset around 1.52 eV, is a result of carrier injection from the GaAs substrate to TI. (b) Helicity-dependent photocurrent 
as a function of excitation photon energy at the normal incidence measured at 5 K from both S1 and S2 samples. The error bars were estimated from the statistics of 300 data points collected in steady-state measurements.
