Abstract
The valence-band structure and the Fermi level (E(F)) position of ferromagnetic-semiconductor GaMnAs are quantitatively investigated by electrically detecting the resonant tunneling levels of a GaMnAs quantum well (QW) in double-barrier heterostructures. The resonant level from the heavy-hole first state is clearly observed in the metallic GaMnAs QW, indicating that holes have a high coherency and that E(F) exists in the band gap. Clear enhancement of tunnel magnetoresistance induced by resonant tunneling is demonstrated in these double-barrier heterostructures.
Highlights
The valence-band structure and the Fermi level (EF) position of ferromagnetic-semiconductor GaMnAs are quantitatively investigated by electrically detecting the resonant tunneling levels of a GaMnAs quantum well (QW) in double-barrier heterostructures
It is assumed that the Fermi level (EF) position is determined by the concentration of the VB holes and that EF lies in VB at 200–300 meV lower than the VB top
Letter, we investigate the resonant levels formed in the metallic GaMnAs QW [16] with a TC value of 60 K, and show that the high coherency of the VB holes is a typical feature of GaMnAs and that EF is not in VB but in the band gap
Summary
The blue and red (green and orange) curves are the data of RTD A (B). The blue or green curves correspond to the parallel magnetization (P). The red or orange curves correspond to the antiparallel magnetization (AP). The shapes of the d2I=dV2-V curves of both RTD A and B are quite similar to those observed in other RTD devices with the various GaMnAs
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