Electrical Study of Ferromagnet Metal Gate MOS Diode: Towards a Magnetic Memory Cell Integrated on Silicon
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0997-I09-04-J07-04
Electrical Study of Ferromagnet Metal Gate MOS Diode: Towards a Magnetic Memory Cell Integrated on Silicon Mehdi Kanoun1, Rabia Benabderrahmane1, Christophe Duluard1, Claire BARADUC1, Nicolas BRUYANT1, HÈrvÈ ACHARD2, and Ahmad BSIESY1,3 1 CEA/SPINTEC, 17 rue des Martyrs, Grenoble, 38054, France 2 CEA/lETI, 17 rue des Martyrs, Grenoble, 38054, France 3 UniversitÈ Joseph Fourier, Grenoble, 38000, France ABSTRACT This work focuses on electrical characterisation of NiFe/SiO2/Si diodes that can be used as spin injection into silicon for future spintronic devices. Capacitance-voltage characteristics show a large increase of the Si/SiO2 interfacial state density compared to Al/SiO2/Si diodes. This result suggests that nickel and/or iron may have diffused across the SiO2 layer. Consistently the current-voltage experimental characteristics can be accounted for by using trap assisted electron transport mechanism. These traps may be attributed to ferromagnet atoms in the oxide bulk.
INTRODUCTION During the last decade, important efforts have been dedicated to MRAM (Magnetic Random Access Memory) research for their high potential as a candidate for a universal memory combining non volatility, speed, endurance and large integration density. Nowadays, all well established memory technologies suffer from certain shortcomings: DRAMs (Dynamic RAMs) are volatile and thereby require standby power. Flash memories are non-volatile, but they exhibit limited write endurance and low write speed. SRAMs (Static RAMs) can be very fast, but they are volatile and have low integration density. The MRAM may overcome these shortcomings since it can potentially combine non-volatility with high read/write speed, endurance and a large integration density. Extensive work was devoted to develop MRAM technology and commercial MRAMs have been recently released by a major semiconductor company [1]. A further development of the MRAM technology would be the integration of magnetic material directly on silicon which may pave the way for new spintronics devices using the CMOS technology [2]. Following this strategy, many works have already showed the possibility to extend spintronics to heterostructures combining ferromagnets and semiconductors [3]. More precisely, efficient spin-polarized electrons injection from a ferromagnet into a semiconductor has been demonstrated by several research groups by using either a reverse-biased Schottky ferromagnet/semiconductor diode [4] or a ferromagnet/insulator/semiconductor diode [5]. In the last case, spin injection takes place by tunnel transport mechanism across an interfacial insulating layer. This tunnel barrier avoids the so-called ìconductivity mismatchî between the ferromagnet and the semiconductor which was identified as a fundamental limit to spin injection [6ñ8]. The originality of our work is the spin injection into silicon, in contrast with the majority of research works, based on III-V semiconductors. However efficient spin injection and collection into silicon requires (i) carrier inj
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