Compensation mechanisms in low-temperature-grown Ga1−xMnxAs investigated by scanning tunneling spectroscopy

Abstract

Ga 1−x Mn x As layers with Mn composition of up to 6.2% are investigated by cross-sectional scanning tunneling microscopy and spectroscopy. We identify in the tunneling spectra contributions from MnGa− acceptor states, compensating AsGa2+ donor states, and additional compensating donor states, which we suggest to be Mni2+ interstitials. On basis of the observed Fermi level shift and a charge carrier compensation analysis, we deduce the concentration of Mni2+ interstitials. Furthermore, scanning tunneling microscopy images suggest an inhomogeneous distribution of Mn dopant atoms.

Infrared survey of the carrier dynamics in III-V digital ferromagnetic heterostructures

“…The top inset corresponds to the metallic random alloys and may be applicable to the DFH sample with y = 10 ML. Depicted in the inset is a fairly broad Mn induced impurity band hybridized with the GaAs valence band, consistent with a number of recent experiments 5,19,23 and band structure calculations. 24 The bottom inset displays the consequence of increasing the GaAs spacer thickness, which results in a reduction of the overlap of the hole wave functions and therefore diminshes the width of the impurity band ͑D͒.…”

Ellipsometric study of the electronic structure ofGa1−xMnxAsand low-temperatureBurch1, Stephens2, Kawakami3 et al. 2004Phys. Rev. B

“…Yet in Ga 1−x Mn x As, as x is increased the Fermi level moves closer to the valence band and the material first becomes fully compensated, then p-type. 10,12,13,37,38 We therefore expect the screening of the potentials to be significantly reduced at low Mn dopings. Then as the number of carriers increases, the effect of the impurities on the band structure should be diminished.…”

“…9 Recent STS and ARPES experiments suggest the Mn form an "impurity band" of d-like states that strongly hybridize with the GaAs valence band. [10][11][12] The ARPES measurements place the occupied d 5 /d 4 levels ≈ 5.3 eV below the valence band maximum (VBM), with the unoccupied d 5 /d 6 level 3.7 eV above the VBM (see Fig. 1).…”

Electronic structure and carrier dynamics of the ferromagnetic semiconductorGa1−xMnxAs<

“…Recent tunneling measurements have shown E F shifting from midgap to the top of the valence band with increased doping. 17 These studies find a significant broadening of the valence band, suggestive of hybridization with a Mn-induced impurity band. Currently little is known about the dynamical properties of conducting holes since the vast majority of experimental studies of Ga 1Ϫx Mn x As are focused on transport measurements in the dc limit.…”