B. D. McCombe, University at Buffalo; DMR 0203560

1. Novel Optical Investigations of Spin Dependent Effects in Semiconductor Nanostructures ~1eV B _ + nm 100/20 120 30 200 AlAs0.15Sb:Be B. D. McCombe, University at Buffalo; DMR 0203560 Injection of spin-polarized carriers into non-magnetic semiconductors is a prerequisite to the success of the emerging field of semiconductor spintronics, where spin transport and manipulation replace and/or augment the charge transport and manipulation of conventional electronic devices. Spin-injection into narrow-gap-semiconductors, such as InAs, is important due to the large coupling of spin and orbital degrees of freedom, which give rise to a variety of spin manipulation schemes. We have shown for the first time spin-injection into InAs measured by an optical technique that probes the circular polarization characteristics of recombination emission from a LED-type structure. We observe a positive polarization degree Pl for a structure with a spin-aligner and a negative Pl for un-polarized injection. This is consistent with calculations based on a rate-equation model that includes finite spin and recombination life-times and the complex band structure of InAs. (work also supported by DARPA/ONR and NSF-ECS 0224225). InAs:Be (University of Würzburg, Germany) InAs CdMnSe:I(1.5% Mn) Spin-LEDs are pro-cessed into mesas (top-emission) Band diagram of spin-LEDs. Spins are polarized in an applied magnetic field by passing through a material with large spin-splitting (CdMnSe) and recombine in InAs with unpolarized holes. Experimental results (squares) and model calcu-lations (lines) for equal spin-flip and recombination times for unpolarized (blue) and polarized (red) injection.

2. Novel Optical Investigations of Spin Dependent Effects in Semiconductor Nanostructures B. D. McCombe, University at Buffalo; DMR 0203560 Education Broader Impact Three graduate students and one undergraduate student have been involved in this work. One Ph.D. student finished in August of this year. He already has several groups in the US and in Europe interested in hiring him for a post-doctoral position. Since 2002, the PI has given two general interest public lectures and one lecture to the Western New York Physics Teachers Association, entitled “What in the world is Spintronics?”, in an effort to demystify this emerging technology and make it understandable to the general public and to high school teachers, and, subsequently, to high school students. New paradigms are needed for future generations of information technology to maintain the remarkable growth of the past several decades, has so pervasively impacted our society. Spintronics is one possible new paradigm, and the electron spin (rather than its charge) is receiving much attention as an another intrinsic property of the electron that can be used for new/improved functionalities in semi-conductor devices. Spin-injection into a narrow-gap material is an essential requirement for the success of this new technology, as these materials provide strong intrinsic mechanisms that permit spin manipulation in “spintronic” device structures.