The photogalvanic current is measured in the unbiased structures at room temperature via a preamplifier and then is recorded by a lock-in amplifier in phase with the PEM. Besides, in order to normalize the data thus enabling a better comparison between BIA and SIA, a common photocurrent j 0 under selleckchem direct current (dc) bias is also measured by a chopper and a lock-in amplifier. Thus, we can use the common photocurrent j 0 as the denominator for normalizing the CPGE current to eliminate the influences of the anisotropic carrier mobility

and carrier density in different directions [26]. For QWs of zinc blende structures grown along the [001] direction, which belongs to C 2v point group symmetry, the Rashba term of the spin-orbital Hamiltonian can be written selleck compound as [2] (1) while the Dresselhaus term is (2) Here, σ is the Pauli spin matrix, k is the in-plane wave vector, α (or β) is the Rashba (or Dresselhaus) spin-orbital parameter, and the coordinate system is x∥ [100] and y∥ [010]. These two Hamiltonians will interfere with each other and result in anisotropic spin splitting in k-space. We can separate the spin splitting induced by Rashba and Dresselhaus terms according to the method suggested in [4, 7], since the Rashba and Dresselhaus terms contribute differently

for particular crystallographic directions. Thus, we can use the geometries shown in Figure 1, i.e., named as geometry CPGE-I shown in Figure 1b and geometry CPGE-II shown in Figure 1c,d, to separate the CPGE current induced by Rashba and Dresselhaus SOC, respectively. In the figures, denotes Resveratrol the direction of light propagation, and j R and j D indicate the CPGE current induced by Rashba and Dresselhaus spin splitting, respectively [4, 7, 26]. Thus, we can obtain j R and j D directly from geometry CPGE-I and obtain the sum and difference of j R and j D from geometry CPGE-II. Therefore, the j R and j D can be obtained separately by the

geometry CPGE-I and CPGE-II, respectively, and then be compared to each other to see whether they are self-consistent [26]. Figure 1 The schematic diagram of the experimental geometries and the spectra of the normalized CPGE current. The schematic diagram for geometries CPGE-I (a) and CPGE-II (b and c). The spectra of the normalized CPGE current obtained by geometry CPGE-II at different angles of incidence (d). The thin lines indicate the sum of j R and j D by the geometry shown in (b), and the thick lines indicate the difference of j R and j D obtained by the geometry shown in (c). All of the spectra are shifted vertically for clarity. In order to get the knowledge of the symmetry of the QW system, we perform reflectance-difference spectrum (RDS) measurement. RDS is an interface-sensitive and nondestructive technique [27, 28], and it can precisely measure the in-plane optical anisotropy (IPOA) between the [110] and directions.