Electrical Spin Injection in Ferromagnetic/Nonmagnetic Semiconductor Heterostructures

As an additional degree of freedom to electronic charge, the manipulation of electronic spin in semiconductor devices is attracting interest due to the possibilities of reading and writing nonvolatile information through magnetism. Here we report the fabrication of all-semiconductor, light-emitting pn junction devices using III-V heterostructures based on GaAs, where electrical spin injection occurs in zero magnetic field from a p-type ferromagnetic semiconductor (Ga,Mn)As into a non-magnetic (In,Ga)As quantum well embedded in GaAs. Spin unpolarized electrons are supplied from n-type GaAs. Injection of spin polarized holes are detected by the polarization of the electroluminescence. The polarization exhibits hysteresis below the ferromagnetic transition temperature of (Ga,Mn)As and the polarization scales with magnetization of the (Ga,Mn)As layer.

Figure 1

Electrical spin injection in an epitaxially-grown ferromagnetic semiconductor heterostructure, based on GaAs. Spontaneous magnetization develops below the Curie temperature in the ferromagnetic p-type semiconductor (Ga,Mn)As. Under forward bias, spin-polarized holes from (Ga,Mn)As and unpolarized electrons from the n-gaAs substrate are injected in the (In,Ga)As quantum well,producing polarized EL

Figure 2

Total electroluminescence intensity of the device under forward bias at temperature T = 6 K and magnetic field H = 1000 Oe is shown (black curve) with its corresponding polarization (red curve).

Figure 3

Hysteretic EL plarization is a direct result of spin injection from the ferromagnetic (Ga,Mn)As layer. Shown are relative change in the energy-integrated polarization, at temperature T = 6-52 K, as a function of in-plane magnetic field. The inset shows the relative remanent EL polarization (symbols) and the temperature dependence of the (Ga,Mn)As magnetic moment measured by a SQUID magnetometer (solid curve), indicating that the EL polarization is propotional to magnetic moment.

Reference
Y. Ohno, D. K. Young, B. Beschoten, F. Matsukura, H. Ohno, and D. D. Awschalom, Nature, vol. 402, pp.790-792, 1999.