The magnetic properties of single and multiple layers of GaMnAs, grown by molecular beam epitaxy, have been investigated for application as spin injector layers in spin polarized lights sources. Curie temperatures, T_c, as high as 150K have been measured in 15nm Ga_(0.95)Mn_(0.05) As films and similar results are obtained for multiple thin layers of GaMnAs separated by 5nm thick GaAs layers. We have also investigated the properties of self-organized InMnAs quantum dots buried in a GaAs or GaMnAs matrix. Magnetization measurements indicate T_c>300K in the dot heterostructures. Light-emitting diode heterostructures with 150nm Ga_(0.95)Mn_(0.05)As spin injector layers and In_(0.4)Ga_(0.6)As quantum dot active regions were grown and fabricated into 600um diameter mesa-shaped surface-emitting devices. Polarized light at l.05u.m is observed with an output polarization efficiency of 26% at a record high temperature.
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