Optical Manipulation of the Rashba Effect in Germanium Quantum Wells

Abstract

The Rashba effect in Ge/Si0.15Ge0.85 multiple quantum wells embedded in a p‐i‐n diode is studied through polarization and time‐resolved photoluminescence. In addition to a sizeable redshift arising from the quantum‐confined Stark effect, a threefold enhancement of the circular polarization degree of the direct transition is obtained by increasing the pump power over a 2 kW cm−2 range. This marked variation reflects an efficient modulation of the spin population and is further supported by dedicated investigations of the indirect gap transition. This study demonstrates a viable strategy to engineer the spin‐orbit Hamiltonian through contactless optical excitation and opens the way toward the electro‐optical manipulation of spins in quantum devices based on group‐IV heterostructures.

Electric-field induced modification of the photoluminescence polarization in Ge/Si0.15Ge0.85 quantum wells

“…The weaker peak shifted to higher energies by 27 meV is the corresponding no-phonon (NP) cL1 − HH1 emission. 12,15,17 Additionally, the low-energy tail of a broad emission from defect states is superimposed on such indirect-gap transitions. Finally, the peak at 0.945 eV is due to the cΓ1 − HH1 optical transition at the center of the Brillouin zone.…”

“…2(a) shows that the ratio between the indirect LA and NP transitions changes markedly with the external bias. 12 The former decreases more rapidly than the latter, opening intriguing questions about electron-phonon interaction. Finally, it can be noticed that the defect tail appears to have lost its spectral weight, thus suggesting a suppression of the carrier recombination events from the defects states.…”

“…A 1-µm-thick Al contact is realized on both the p-and n-layers through a final lithographic step. 12 The well and barrier thicknesses were obtained via high resolution x-ray diffraction (HRXRD). The measurements were performed by means of a PANalytical X'Pert PRO diffractometer.…”

“…As opposed to III-V compounds, 11 such a possibility has received little attention in the context of heterostructures made of group-IV materials. 12,13 In this work we present a polarization-resolved photoluminescence (PL) study of p-i-n diode structures in which the intrinsic region consists of a repetition of 50 Ge QWs and Si 0.15 Ge 0.85 barriers. Different excitation power densities are investigated in a reverse bias regime.…”

“…Our work presents a starting point to deepen the understanding of spin-dependent properties in group IV heterostructures and their control by accessible means. 12…”