Spin-polarized electron transport processes at the ferromagnet/semiconductor interface

TY - JOUR

T1 - Spin-polarized electron transport processes at the ferromagnet/semiconductor interface

AU - Hirohata, A.

AU - Bland, J.A.C.

AU - Xu, Y.B.

AU - Guertler, C.M.

AU - Holmes, S.N.

N1 - © 2000 IEEE. Personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution to servers or lists, or to reuse any copyrighted component of this work in other works must be obtained from the IEEE.

PY - 2000/9

Y1 - 2000/9

N2 - Circularly polarized light was used to excite electrons with a spin polarization perpendicular to the film plane in ferromagnet/semiconductor hybrid structures. The Schottky characteristics at the interface were varied by using NiFe, Co and Fe as the ferromagnet. The Schottky characteristics were clearly observed with NiFe and Co/GaAs, while almost ohmic I-V characteristics were seen with Fe/GaAs. At negative bias a helicity-dependent photocurrent, dependent upon the magnetization configuration of the film and the Schottky barrier height, was detected upon modulating the polarization from right to left circular, For the magnetization along or perpendicular to the surface normal, the helicity-dependent photocurrent In or I 0, respectively, was measured. The asymmetry P=(In-I0)/(In+I0) of the helicity-dependent photocurrent decreases upon increasing the doping density of the GaAs substrates. P also decreases with photon energy h¿ as found for the polarization of photoexcited electrons in GaAs. In NiFe/GaAs samples for h¿=1.59 eV, P=16% for n+=1023 m-3 and P=-23% for p-=1025 m-3 doped substrates, i.e. P is comparable in magnitude to the theoretically predicted spin polarization of 50% for the optically pumped conduction band in GaAs. The results provide unambiguous evidence of spin-polarized electron transport through the ferromagnet/semiconductor interface and show that the Schottky barrier height controls the spin-polarized electron current passing from the semiconductor to the ferromagnet. The asymmetry data indicates that spin-polarized electrons are transmitted from the semiconductor to the ferromagnet with a high efficiency.

AB - Circularly polarized light was used to excite electrons with a spin polarization perpendicular to the film plane in ferromagnet/semiconductor hybrid structures. The Schottky characteristics at the interface were varied by using NiFe, Co and Fe as the ferromagnet. The Schottky characteristics were clearly observed with NiFe and Co/GaAs, while almost ohmic I-V characteristics were seen with Fe/GaAs. At negative bias a helicity-dependent photocurrent, dependent upon the magnetization configuration of the film and the Schottky barrier height, was detected upon modulating the polarization from right to left circular, For the magnetization along or perpendicular to the surface normal, the helicity-dependent photocurrent In or I 0, respectively, was measured. The asymmetry P=(In-I0)/(In+I0) of the helicity-dependent photocurrent decreases upon increasing the doping density of the GaAs substrates. P also decreases with photon energy h¿ as found for the polarization of photoexcited electrons in GaAs. In NiFe/GaAs samples for h¿=1.59 eV, P=16% for n+=1023 m-3 and P=-23% for p-=1025 m-3 doped substrates, i.e. P is comparable in magnitude to the theoretically predicted spin polarization of 50% for the optically pumped conduction band in GaAs. The results provide unambiguous evidence of spin-polarized electron transport through the ferromagnet/semiconductor interface and show that the Schottky barrier height controls the spin-polarized electron current passing from the semiconductor to the ferromagnet. The asymmetry data indicates that spin-polarized electrons are transmitted from the semiconductor to the ferromagnet with a high efficiency.

KW - ferromagnet/semiconductor interface

KW - photon helicity

KW - Schottky barrier

KW - spin-polarized electron

U2 - 10.1109/20.908601

DO - 10.1109/20.908601

M3 - Article

SN - 0018-9464

VL - 36

SP - 2827

EP - 2832

JO - IEEE Transactions on Magnetics

JF - IEEE Transactions on Magnetics

IS - 5 (Part 1)

ER -