Tunable spin-tunnel contacts to silicon using low-work-function ferromagnets

Magnetic tunnel junctions have become ubiquitous components appearing in magnetic random-access memory, read heads of magnetic disk drives and semiconductor-based spin devices. Inserting a tunnel barrier has been key to achieving spin injection from ferromagnetic (FM) metals into GaAs, but spin injection into Si has remained elusive. We show that Schottky barrier formation leads to a huge conductivity mismatch of the FM tunnel contact and Si, which cannot be solved by the well-known method of adjusting the tunnel barrier thickness. We present a radically different approach for spin-tunnelling resistance control using low-work-function ferromagnets, inserted at the FM/tunnel barrier interface. We demonstrate that in this way the resistance–area (RA) product of FM/Al2O3/Si contacts can be tuned over eight orders of magnitude, while simultaneously maintaining a reasonable tunnel spin polarization. This raises prospects for Si-based spintronics and presents a new category of ferromagnetic materials for spin-tunnel contacts in low-RA-product applications.

[1]  B. Tsaur,et al.  Low Schottky barrier of rare‐earth silicide on n‐Si , 1981 .

[2]  Daniel J. Connelly,et al.  Fermi-level depinning for low-barrier Schottky source/drain transistors , 2006 .

[3]  G. Schmidt,et al.  Fundamental obstacle for electrical spin injection from a ferromagnetic metal into a diffusive semiconductor , 1999, cond-mat/9911014.

[4]  M. Julliere.  Tunneling between ferromagnetic films , 1975 .

[5]  W. E. Beadle,et al.  Quick reference manual for silicon integrated circuit technology , 1985 .

[6]  S. Sugahara,et al.  Spin metal-oxide-semiconductor field-effect transistors (spin MOSFETs) for integrated spin electronics , 2005 .

[7]  Jon M. Slaughter,et al.  Magnetoresistive random access memory using magnetic tunnel junctions , 2003, Proc. IEEE.

[8]  S. Yuasa,et al.  Giant room-temperature magnetoresistance in single-crystal Fe/MgO/Fe magnetic tunnel junctions , 2004, Nature materials.

[9]  S. Chou,et al.  Spin-valve effects in nickel/silicon/nickel junctions , 1996 .

[10]  Albert Fert,et al.  Conditions for efficient spin injection from a ferromagnetic metal into a semiconductor , 2001 .

[11]  H. Brückl,et al.  Magnetic moment compensation in exchange-biased trilayers with antiparallel spin alignment , 2003 .

[12]  E. Rashba.  Theory of electrical spin injection: Tunnel contacts as a solution of the conductivity mismatch problem , 2000, cond-mat/0010473.

[13]  Interrelation of Work Function and Surface Stability: The Case of BaAl4 , 2005, physics/0505176.

[14]  S. Sarma,et al.  Spintronics: Fundamentals and applications , 2004, cond-mat/0405528.

[15]  Kinder,et al.  Large magnetoresistance at room temperature in ferromagnetic thin film tunnel junctions. , 1995, Physical review letters.

[16]  J. Boeck,et al.  Spin injection in LED's and in unipolar devices , 2006 .

[17]  S. M. Sze.  Physics of semiconductor devices /2nd edition/ , 1981 .

[18]  H. Michaelson.  The work function of the elements and its periodicity , 1977 .

[19]  C. Marcus,et al.  Spin polarized tunneling at finite bias. , 2005, Physical review letters.

[20]  C. Carbone,et al.  FORMATION OF A FERROMAGNETIC SILICIDE AT THE FE/SI(100) INTERFACE , 1997 .

[21]  Tunneling measurements of conduction-electron-spin polarization in heavy rare-earth metals , 1980 .

[22]  D. Awschalom,et al.  Resonant Spin Amplification in n-Type GaAs , 1998 .

[23]  B. Jonker,et al.  Progress toward electrical injection of spin-polarized electrons into semiconductors , 2003, Proc. IEEE.

[24]  S. Datta,et al.  Electronic analog of the electro‐optic modulator , 1990 .

[25]  R M Macfarlane,et al.  Highly spin-polarized room-temperature tunnel injector for semiconductor spintronics using MgO(100). , 2005, Physical review letters.

[26]  A. Panchula,et al.  Giant tunnelling magnetoresistance at room temperature with MgO (100) tunnel barriers , 2004, Nature materials.

[27]  Byong‐Guk Park,et al.  Temperature dependence of magnetocurrent in a magnetic tunnel transistor , 2005 .

[28]  Stuart A. Wolf,et al.  Spintronics : A Spin-Based Electronics Vision for the Future , 2009 .

[29]  O.M.J. van 't Erve,et al.  Comparison of Fe/Schottky and Fe/Al2O3 tunnel barrier contacts for electrical spin injection into GaAs , 2004 .

[30]  T. Miyazaki,et al.  Giant magnetic tunneling e ect in Fe/Al2O3/Fe junction , 1995 .

[31]  D. Awschalom,et al.  Lateral drag of spin coherence in gallium arsenide , 1999, Nature.

[32]  V.F.Motsnyi,et al.  Electrical spin injection in a ferromagnet/tunnel barrier/semiconductor heterostructure , 2002 .

[33]  D. K. Young,et al.  Electrical spin injection in a ferromagnetic semiconductor heterostructure , 1999, Nature.

[34]  John Bardeen,et al.  Surface States and Rectification at a Metal Semi-Conductor Contact , 1947 .

[35]  C. Adelmann,et al.  Imaging Spin Transport in Lateral Ferromagnet/Semiconductor Structures , 2005, Science.

[36]  R. Fiederling,et al.  Injection and detection of a spin-polarized current in a light-emitting diode , 1999, Nature.

[37]  B. Tsaur,et al.  Contact reaction between Si and rare earth metals , 1981 .

[38]  S. M. Sze,et al.  Physics of semiconductor devices , 1969 .