Effects of Device Geometry on Output Circular Polarization in a Spin-LED

A surface emitting spin-polarized light emitting diode (Spin-LED) is considered for the study of the device geometry dependence of the output circular polarization It is found that the output circular polarization is maximum at the outer region of the circular non-FM Ohmic contact to the p-region, which delineates radial extent of the active region in the intrinsic layer. We observe that the output circular polarization increase as a function of the p-contact radius when the contact size is small but for large values of the p-contact radius the reverse trend is noted. An enhancement of the spin diffusion length increases the degree of polarization of the emitted circular light. The enhancement however is observed to fall off for still higher values of spin lifetime.