Bias dependence of spin injection into GaAs from Fe, FeCo, and (Ga,Mn)As contacts

Abstract

Spin injection from Fe(001) and (Ga,Mn)As(001) into n-GaAs(001) was investigated using a method which provides two-dimensional cross-sectional images of the spin polarization in GaAs. While the distribution of the spin polarization below the injecting contact is nearly uniform for (Ga,Mn)As, a strong confinement near the contact edge is observed for Fe and FeCo. The spin polarization in GaAs changes sign when the injected current is reversed. Multiple sign reversals as a function of bias voltage as reported previously for Fe injectors are not observed with (Ga,Mn)As and Fe contacts grown on clean n þþ ÀGaAs in agreement with earlier results for an epitaxial FeCo injector.

Optical investigation of electrical spin injection into an inverted two-dimensional electron gas structure

“…Finally, the sample is cleaved in the [110] direction along the transport channel, reducing the channel width to 40 μm. This exposes the (110) surface, which enables direct magneto-optical access to the spin accumulation underneath the injecting contacts [10][11][12][13]. We investigate samples from two different wafers, called sample A and sample B in the following.…”

Demonstration of the spin solar cell and spin photodiode effect

“…This ensures that the quasi-static magnetization of the ferromagnetic contacts does not contribute to the Kerr signal171819. In addition, to eliminate any electro-optic Kerr rotation, the measurements are performed in remanence after saturating the magnetization along [1–10] and [−110], respectively.…”

“…In Sample A, both effects are demonstrated by using a laser beam simultaneously to generate electron-hole pairs and to detect spin accumulation via the polar magneto-optic Kerr effect. We employ a cross-sectional two-dimensional imaging method that allows probing the spin polarization also below the ferromagnetic contacts at cryogenic temperatures171819. For the optical detection, a modulation technique is used, so that the Kerr rotation θ K is strictly proportional to the spin accumulation in the n-GaAs channel at the laser spot position ( is the chemical potential for up/down spin electrons).…”

Nonuniform current and spin accumulation in a 1 μm thick n-GaAs channel

“…This becomes obvious by comparing fitting results of Hanle data from a one-and a two-dimensional model. For our studies we employ a cross-sectional imaging method that allows to probe the two-dimensional spin polarization distribution even below the contacts 8,9 and compare the experimental results to two-dimensional drift-diffusion simulations.…”

“…A square-wave bias voltage alternating between zero and V B is applied between the contacts and the Kerr rotation is detected synchronously with balanced photo-receivers and a lock-in technique. This ensures that the (quasistatic) magnetization of the ferromagnetic contacts does not contribute to the Kerr signal 8,9 . Fig.…”