Even though the strong Fermi-level pinning at the metal/germanium (Ge) interface can be alleviated by inserting a thin layer of tunneling oxide, the still sizeable Schottky barriers and the wide depletion regions of the Fe/oxide/ contacts make the junction resistances strongly dependent of temperature. The resistance-area (RA) products of these junctions are too high for spin injection and cannot be tuned by simply varying oxide thickness or using ferromagnetic metal (FM) with a lower work function. In this work, low energy ion implantation and rapid thermal annealing were utilized to degenerately dope the Ge surface layer to facilitate single-step tunneling transport. The RA products of the junctions with surface doping are significantly reduced and weakly dependent of temperature. This method gives a prospect for spin injection to Ge from FM.
Engineering of tunnel junctions for prospective spin injection in germanium
Yi Zhou, Masaaki Ogawa, Mingqiang Bao, Wei Han, Roland K. Kawakami, Kang L. Wang; Engineering of tunnel junctions for prospective spin injection in germanium. Appl. Phys. Lett. 15 June 2009; 94 (24): 242104. https://doi.org/10.1063/1.3157128
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