Room-temperature spin photocurrent spectra at interband excitation and comparison with reflectance-difference spectroscopy in InGaAs/AlGaAs quantum wells

Abstract

Spectra of the interband spin photocurrent due to Rashba and Dresselhaus spin splittings have been experimentally investigated in InGaAs/AlGaAs quantum wells at room temperature. The Rashba- and Dresselhaus-induced circular photogalvanic effect (CPGE) spectra are found to be quite similar in the spectral regions corresponding to the transitions 1e1hh (the first conduction to the first valence sub-band of heavy hole) and 1e2hh. The ratio of Rashba- and Dresselhaus-induced CPGE currents for the transition 1e1hh is estimated to be 4.95. The magnitude of the Rashba-induced CPGE current is up to several tens of nA/W for the transition 1e1hh, which is 1 order of magnitude larger than that obtained in GaN/AlGaN superlattices. Comparing the CPGE spectrum with reflectance-difference and photoreflectance spectra, we find that the large Rashba spin splitting is mainly induced by a large indium atom segregation effect and by the internal field in the quantum wells.

Femtosecond Circular Photon Drag Effect in the Ag/Pd Nanocomposite

“…CPGE provided information on the spin–orbit coupling and has been observed in crystalline bismuth silicate (Bi 12 SiO 20 ) [15], lead germanate (Pb 5 Ge 3 O 11 ) [16], lithium niobate [17], indium nitride (InN) films [10, 11], quantum wells [4, 7, 8, 18–20] and 2D heterostructures [9, 21]. …”

Spin photocurrent spectra induced by Rashba- and Dresselhaus-type circular photogalvanic effect at inter-band excitation in InGaAs/GaAs/AlGaAs step quantum wells

“…All epilayers are intentionally undoped and the InGaAs layers are fully strained since their thickness is far below the critical thickness. The sample is cleaved along [110] and [1$\overline{1}$0] (denoted as the x ′ and y ′ directions, respectively) into a square of 5 mm × 5 mm with four pairs of ohmic contacts 4 mm apart along the x ′ , y ′ and diagonal directions, respectively, as shown in figure one(a) in [26]. The ohmic contacts are made by indium deposition and annealed at about 420°C in nitrogen atmosphere.…”

Helicity dependent photocurrent enabled by unpolarized radiation in a GaAs/Al0.3Ga0.7As two-dimensional electron system

“…For a 2DEG system of C 2v symmetry, the CPGE current can be excited by obliquely incident radiation as an odd function of the incident angle and vanishes at normal incidence. [13][14][15][16][17][18] In our investigation, we align the circularly polarized near-infrared radiation perpendicularly to the plane of a (001)-oriented GaAs/Al 0.3 Ga 0.7 As 2DEG to suppress the CPGE in the system and synchronously illuminate the system obliquely with an additional unpolarized radiation above the GaAs bandgap. We observe a helicity dependent photocurrent recovered due to the assistant radiation under suppressed configuration of CPGE.…”

“…The CPGE photocurrent is generally attributed to Rashba and Dresselhaus effect which could be separated experimentally. [12][13][14][15]17,18 The Rashba and Dresselhaus effect are correlated with the inversion asymmetry of the system, so-called structure inversion asymmetry (SIA) and bulk IA (BIA), respectively. The SIA and BIA induce k-linear terms in the Hamiltonian of a two-dimensional system, which could give rise to a net current.…”

“…The radiation emitted from the laser passes through a 45 -oriented polarizer and a photoelastic modulator (PEM) to yield a periodically oscillating polarization state between right-and left-hand circularly polarization. 15,17 The circularly polarized radiation induces electric current at zero bias and the electric signals are picked up by the lock-in amplifier in phase with the PEM. The excitation photon energy (1.17 eV) is below the bandgap of GaAs (1.42 eV), we could nevertheless attribute the optical transition to be interband regime according to the Franz-Keldysh effect 19,20 (see Fig.…”