Site-specific atomic order and band structure tailoring in the diluted magnetic semiconductor (In,Ga,Mn)As

Abstract

Diluted ferromagnetic semiconductors combining ferromagnetic and semiconducting properties in one material provide numerous new functionalities, attractive for basic studies and potentially useful for novel device applications. The tailoring of the electronic structure in analogy to conventional semiconductors has yet to be explored. Here, we demonstrate the conservation of broken inversion symmetry and band structure tailoring for high-quality molecular-beam-epitaxy-grown (In,Ga,Mn)As films with 3% In plus 2.5% or 5.6% Mn using hard-x-ray photoelectron diffraction (hXPD) and momentum microscopy. Photon energies of 3-5 keV ensure that the results are not corrupted by surface effects, which are known to be strong in semiconductors. The missing inversion center of the GaAs host lattice leads to fingerprint-like hXPD signatures of As and Ga sites. For both concentrations, Mn predominantly occupies Ga substitutional sites. Momentum microscopy reveals a shift of the chemical potential with increasing Mn doping and a highly dispersing band, crossing the Fermi level for high Mn concentration. The Mn doping induces a pronounced modification of the spin-orbit split-off band.

Time-of-flight photoelectron momentum microscopy with 80–500 MHz photon sources: electron-optical pulse picker or bandpass pre-filter

“…Parallel acquisition of many energies minimizes the radiation dose for sensitive samples (Giangrisostomi et al, 2018), reduces the dataacquisition time in photon-hungry experiments in the soft- (Medjanik et al, 2017) and hard-X-ray range (Medjanik et al, 2019), and enables full-field XPD (Fedchenko et al, 2019). First studies indicate that the latter method has a huge potential for in situ structural analysis (Fedchenko et al, 2020;Medjanik et al, 2021;Hoesch et al, 2021), in particular in the ultrafast regime at FELs (Kutnyakhov et al, 2020;Dendzik et al, 2020;Curcio et al, 2021;Pressacco et al, 2021). XPD measurements are an indispensable prerequisite for aberration-free bulk band mapping using hard X-rays Medjanik et al, 2021;Babenkov et al, 2019;Scho ¨nhense et al, 2020a).…”

“…First studies indicate that the latter method has a huge potential for in situ structural analysis (Fedchenko et al, 2020;Medjanik et al, 2021;Hoesch et al, 2021), in particular in the ultrafast regime at FELs (Kutnyakhov et al, 2020;Dendzik et al, 2020;Curcio et al, 2021;Pressacco et al, 2021). XPD measurements are an indispensable prerequisite for aberration-free bulk band mapping using hard X-rays Medjanik et al, 2021;Babenkov et al, 2019;Scho ¨nhense et al, 2020a). In combination with an imaging spin filter, the 3D-recording architecture enables accessing a full spin texture in reasonable time (Elmers et al, 2016(Elmers et al, , 2020bVasilyev et al, 2020;Chernov et al, 2021).…”

“…The finite size of the selector aperture does not influence the resolution in the XPD image because for the angle-encoded diffraction pattern a small parallel shift of the beam inside of the aperture ($ 100 mm) is insignificant for the momentum image on the DLD (40 mm diameter). A calculated W 4f XPD pattern for W(110) is shown in inset (e2); for details on the Bloch-wave model, see Fedchenko et al (2019Fedchenko et al ( , 2020 and Medjanik et al (2021). The calculated pattern shows many more details, which reflects that at 500 eV the Bloch-wave model is at its lower limit of the validity range.…”

“…The high site specificity of hXPD (Fedchenko et al, 2020) can be exploited as a unique fingerprint of atomic sites in compounds. The first applications of this young technique for the analysis of Mn dopant sites in the diluted ferromagnetic semiconductor (GaMnIn)As (Medjanik et al, 2021) and Te in the Si lattice in the hyperdoped regime (Hoesch et al, 2021) shine a first light on the potential of hXPD. Electronic and structural information can be obtained in a single experiment and under identical conditions (kinetic energy of the photoelectrons, size and position of the probing spot, probing depth).…”

“…Electronic and structural information can be obtained in a single experiment and at identical conditions (kinetic energy of the photoelectrons, size and position of the probing spot, probing depth). In turn, this allows eliminating the strong hXPD patterns imprinted on the valence-band momentum images in hard X-ray ARPES (HARPES), allowing mapping of intensitycorrected valence bands [22,23,11,20]. A time-resolved variant of ToF-MM with fs-pulsed sources was recently established at the free electron laser FLASH at DESY, Hamburg [24][25][26].…”