Co - Fe - B/MgO/

Abstract

We report on the growth and study of Co-Fe-B/MgO/Ge(001) spin photodiode by using a combination of both molecular beam epitaxy (MBE) and sputtering methods. An epitaxial growth of MgO on Ge in MBE is achieved by the deposition of MgO at room temperature (RT) followed by a post-growth annealing at 300°C. The spin detector, which consists of 1.1-nm ultrathin Co-Fe-B layer capped with 5-nm Ta is subsequently grown by sputtering at RT. After a post-growth annealing of the whole structure at 250°C, we obtain clear evidence of a strong perpendicular magnetic anisotropy in the temperature range 10-300 K. Co-Fe-B/MgO/Ge(001) heterojunctions are then processed into spin photodiodes demonstrating at zero magnetic field a photocurrent helicity asymmetry of about 0.9% at 9 K and 0.1% at RT at the telecommunication wavelength of 1310 nm. The demonstration of a spin photodiode working at a telecommunication wavelength with zero applied magnetic field is of great interest for future applications of the optical transport of spin information.

Recombination Time Mismatch and Spin Dependent Photocurrent at a Ferromagnetic-Metal–Semiconductor Tunnel Junction

“…The electrical signal is subsequently detected thanks to spin-dependent photocurrent, resulting from transport phenomena in all-semiconductor devices [8,9] or tunneling into a ferromagnetic (FM) contact. However, the realization of efficient spin photodiodes remains * henri-jean.drouhin@polytechnique.edu a challenge for more than two decades [1,[8][9][10][11][12][13][14][15][16][17][18][19][20][21] and the underlying physics remains far from a clear understanding. While a variety of materials and structures have the ability to produce helicity-dependent signals, potential devices are based on the combination of well-mastered materials and technologically-mature heterostructures, suited for room temperature operation [1], e.g.…”

Electrical detection of light helicity using a quantum-dot-based hybrid device at zero magnetic field

“…This new generation of devices could be also very useful for memory-based devices with an optical reading of information stored in the ferromagnetic layer. Several works have been published dealing with such helicity-sensitive detectors based on metal-oxidesemiconductor junctions [27][28][29][30] or spin-LEDs [31][32][33]. There are three key issues to obtain an efficient helicity detector.…”

“…Up to now, most of the studies have been performed using external magnetic fields on the order of 1 T [28,29,31] to align the magnetization of the electrode along the growth direction of the structure in order to obey the condition imposed by the optical selection rules in the semiconductor [34]. Among these studies, a few of them were realized at zero external magnetic field using PMA detectors [30,33,35] or in-plane detectors [32,36] under oblique incidence angle. Thirdly, it is also important to have a carrier recombination channel [31,37] that is competitive with the extraction channel from the semiconductor to the ferromagnetic electrode, in order to get an helicity asymmetry of the photocurrent under circularly polarized light in continuous-wave (cw) experiments.…”

“…This new generation of devices could be also very useful for memory-based devices with an optical reading of information stored in the ferromagnetic layer. Several works have been published dealing with such helicity sensitive detectors based on metal-oxide-semiconductor (MOS) junctions [26]- [29] or Spin-LEDs used under reversed bias (through the paper, we define the qualification reversed bias with respect to the p-i-n junction, and not relative to the magnetic tunnel injector and ferromagnetic metallic electrode) [30]. The key issues to obtain an efficient helicity detector are: (i) an electron spin relaxation time in the semiconductor part long enough such that the spin is maintained until the carrier crosses the tunnel barrier before to be collected by the ferromagnetic electrode, (ii) the ability to work at zero magnetic field for a realistic device.…”