Electrical spin injection from an n-type ferromagnetic semiconductor into a III–V device heterostructure

Abstract

The use of carrier spin in semiconductors is a promising route towards new device functionality and performance. Ferromagnetic semiconductors (FMSs) are promising materials in this effort. An n-type FMS that can be epitaxially grown on a common device substrate is especially attractive. Here, we report electrical injection of spin-polarized electrons from an n-type FMS, CdCr(2)Se(4), into an AlGaAs/GaAs-based light-emitting diode structure. An analysis of the electroluminescence polarization based on quantum selection rules provides a direct measure of the sign and magnitude of the injected electron spin polarization. The sign reflects minority rather than majority spin injection, consistent with our density-functional-theory calculations of the CdCr(2)Se(4) conduction-band edge. This approach confirms the exchange-split band structure and spin-polarized carrier population of an FMS, and demonstrates a litmus test for these FMS hallmarks that discriminates against spurious contributions from magnetic precipitates.

InGaAs spin light emitting diodes measured in the Faraday and oblique Hanle geometries

“…In similar systems optical polarizations of 30% have been measured [11,12,26]. The lower value seen here is consistent with the relatively small spin lifetimes that we extract from the Hanle effect.…”

“…Using time-resolved photoluminescence on an equivalent undoped sample the electron lifetime was determined as 400 ps at 4 K. This allows the interfacial injection polarization, S 0Y , to be estimated as 50 ± 20% at 4 K, which is in line with other measurements [11,12,26] and the expected spin-polarization of Fe [27].…”

“…Fe spin-injecting contacts, with a bulk polarization of ~40%, have provided the highest spin-injection polarizations of all the simple metals. Fe is closely lattice matched to GaAs and the interface between these materials has been studied in depth [9][10][11][12][13]. However, standard growth procedures that involve removing the semiconductor wafer from ultrahigh vacuum (UHV), add unwanted impurities at the interface with a magnetic contact.…”

Detection of Current-Induced Spins by Ferromagnetic Contacts

“…It is possible to reduce critical currents strongly by reducing the magnetization of FM. This can be achieved by choosing a ferromagnetic semiconductor (that should be n-type in the case of InAs [33]) that is furthermore close to its Curie temperature [34]. Excessive heating can be avoided by short-time pulses [34].…”

Probing the Local Coordination Environment for Transition Metal Dopants in Zinc Oxide Nanowires

“…These materials are envisioned to have potential use in so-called "spintronic" devices, in which one seeks to control both the charge and spin degrees of freedom of the electron; a few such prototypical devices are already in existence. 1,2 Despite improvements in device fabrication, the fundamental questions regarding the origins of the magnetic behavior in dilute magnetic semiconducting (DMS) systems remain unsatisfactorily answered. It is known that much of the controversy has stemmed from the fact that clustering or phase separation of the magnetic dopant ions can result in magnetic data that is misleading or unreliable.…”