Spin Injection From The Heusler Alloy Co2MnGe INTO Al0.1Ga0.9As/GaAs Heterostructures

The Heusler alloy Co$_{2}$MnGe has been predicted to be half- metallic [1]. The ability to grow Co$_{2}$MnGe epitaxially on GaAs, the predicted half-metallicity and the high Curie temperature ($\sim $900K), make it an ideal candidate for a spin injecting contact. Co$_{2}$MnGe epitaxial films were grown by molecular beam epitaxy (MBE) on Al$_{x}$Ga$_{1­x}$As (001) surfaces. \textit{In-situ} and \textit {ex-situ} structural characterization, such as RHEED, XRD and TEM, demonstrate the epitaxial single crystallinity of the films. In order to measure the spin injection, tunneling Schottky barrier contact spin-LED structures were fabricated from MBE-grown Al/Co$_{2}$MnGe(70{\AA})/$n$-Al$_{0.1}$Ga$_{0.9}$As/ GaAs(100{\AA})/$p$-Al$_{0.1}$Ga$_{0.9}$As heterostructures. The epitaxial heterostructures were processed into LED devices and the devices were operated with the Schottky contact under reverse bias and the $p-i-n$ LED under forward bias. Electroluminescence was collected along the sample normal. The circular polarization of the observed electroluminescence was 14 {\%} indicating a spin injection of 14{\%} at 2K. The injected spin polarization at 2 K was calculated to be 27 {\%} based on a calibration of the spin detector using Hanle effect measurements. The authors thank NSF-MRSEC, DARPA, and ONR for financial support. [1] S. Fujii, S. Sugimura, S. Ishida, and S. Asano., J. Phys.:Condens. Matter 2, 8583 (1990).