| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2000: ¥1,000,000 (Direct Cost: ¥1,000,000)
Fiscal Year 1999: ¥2,600,000 (Direct Cost: ¥2,600,000)
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| Research Abstract |
In order to inject spin-polarized electrical current into semiconductors, we fabricated ferromagnetic/nonmagnetic semiconductor heterostructures by employing MBE regrowth technique, and investigated their current-voltage characteristics and electroluminescence polarization. The summary of the research results is as follows :
Electrical spin injection into nonmagnetic semiconductor is successfully achieved in ferromagnetic semiconductor (Ga, Mn) As/nonmagnetic semiconductor (In, Ga) As pn junction light emitting diodes prepared by molecular beam epitaxy. We observed hysteretic polarization in electroluminescence spectra of ferromagnetic/nonmagnetic pn junction. The degree of the remanent electroluminescence polarization was about ±1%, of which the temperature dependence is almost proportional to that of the magnetization of (Ga, Mn) As.
We fabricated ferromagnetic (Ga, Mn) As/nonmagnetic (In, Ga) As semiconductor light emitting diodes, which are grown on lattice-relaxed n-In_xGa_<1-x>As (
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x=0.15-0.18) buffer layer so that the magnetic easy axis of (Ga, Mn) As directs perpendicular to the plane. We measured the degree of the polarization of light emitted from the backside of the substrate, and observed hysteretic polarization.
In order to clarify the valence band alignment at (Ga, Mn) As/GaAs heterointerface, we fabricated (Ga, Mn) As/i-GaAs/p-GaAs p-i-p structures with different Mn concentration in (Ga, Mu) As, and measured the temperature dependence of current-voltage characteristics of them. It is found that the current-voltage characteristics of such p-i-p structures depend on the polarity of bias voltage, which suggest the existence of a potential barrier at the interface when hole current is injected from (Ga, Mn) As into GaAs. Assuming that the current is dominated by thermal emission over a Schottky barrier, we analyzed the results and found that the barrier height measured from the Fermi energy of (Ga, Mn) As is about 100 meV, which does not depend on the Mn concentration in (Ga, Mn) As. Less
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