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High current gain silicon-based spin transistor

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  • Physics


INSTITUTE OF PHYSICS PUBLISHING JOURNAL OF PHYSICS D: APPLIED PHYSICS J. Phys. D: Appl. Phys. 36 (2003) 81–87 PII: S0022-3727(03)56148-4 High current gain silicon-based spin transistor C L Dennis1,4, C Sirisathitkul1,5, G J Ensell2, J F Gregg1 and S M Thompson3 1 Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, UK 2 Department of Electronics and Computer Science, University of Southampton, Southampton SO17 1BJ, UK 3 Department of Physics, University of York, York, YO10 5DD, UK E-mail: [email protected] Received 15 November 2002 Published 30 December 2002 Online at Abstract A silicon-based spin transistor of novel operating principle has been demonstrated in which the current gain at room temperature is 1.4 (n-type) and 0.97 (p-type). This high current gain was obtained from a hybrid metal/semiconductor analogue to the bipolar junction transistor which functions by tunnel-injecting carriers from a ferromagnetic emitter into a diffusion driven silicon base and then tunnel-collecting them via a ferromagnetic collector. The switching of the magnetic state of the collector ferromagnet controls the collector efficiency and the current gain. Furthermore, the magnetocurrent, which is determined to be 98% (140%) for p-type (n-type) in −110 Oe, is attributable to the spin-polarized base diffusion current. 1. Introduction Since the discovery of giant magnetoresistance (GMR) [1] in 1988, interest has been steadily growing in magnetically sensitive devices. This has resulted in several attempts to fabricate spin transistors that exploit the spin dependent scattering of charge carriers to yield a device with high current gain and high magnetic sensitivity. The first such attempt was Johnson’s all-metal three-terminal device [2], which added a third terminal to the middle paramagnetic layer of a GMR multilayer. The electrical characteristics of this purely Ohmic device are magnetically tunable, but, due to its all-metal

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