Optical Detection of Hot-Electron Spin Injection into GaAs from a Magnetic Tunnel Transistor Source

Injection of spin-polarized hot-electron current from a magnetic tunnel transistor into GaAs is demonstrated by the observation of polarized light emission from a $\mathrm{G}\mathrm{a}\mathrm{A}\mathrm{s}/{\mathrm{I}\mathrm{n}}_{0.2}{\mathrm{G}\mathrm{a}}_{0.8}\mathrm{A}\mathrm{s}$ multiple quantum well light-emitting diode. Electroluminescence from the quantum wells shows a polarization of $\sim 10\%$ after subtraction of a linear background polarization. The polarization shows a strong dependence on the bias voltage across the diode, which may originate from changes in the electron spin relaxation rate in the quantum wells under varying bias conditions.