Detection of electrical spin injection by light-emitting diodes in top- and side-emission configurations

Detection of the degree of circular polarization of the electroluminescence of a light-emitting diode (LED) fitted with a spin injecting contact (a spin-LED) allows the direct determination of the spin polarization of the injected carriers. Here, we compare the detection efficiency of (Al,Ga)As spin-LEDs fitted with a (Zn,Be,Mn)Se spin injector in top- and side-emission configurations. In contrast to top emission, we cannot detect the electrical spin injection in side emission by analyzing the degree of circular polarization of the electroluminescence. To reduce resonant optical pumping of quantum-well excitons in side emission, we have analyzed structures with mesa sizes as small as 1 mum. (C) 2003 American Institute of Physics.