Search

Ge two-dimensional hole gases in strained modulation-doped quantum-wells represent a promising material platform for future spintronic applications due to their excellent spin transport properties and the theoretical possibility of efficient spin manipulation. Due to the continuous development of epitaxial growth recipes extreme high hole mobilities and low effective masses can be achieved, promising an efficient spin transport. Furthermore, the Ge two-dimensional hole gas (2DHG) can be integrated in the well-established industrial complementary metal-oxide-semiconductor (CMOS) devices technology. However, efficient electrical spin injection into a Ge 2DHG - a prerequisite for the realization of spintronic devices - has not yet been demonstrated. In this work, we report the fabrication and low-temperature magnetoresistance measurements of a laterally structured Mn5Ge3/Ge 2DHG/ Mn5Ge3 device. The ferromagnetic Mn5Ge3 contacts are grown directly into the Ge quantum well by means of an interdiffusion process with a spacing of approximately 130 nm. We observe a magnetoresistance signal for temperatures below 13 K possibly arising from successful spin injection. The results represent a step forward toward the realization of CMOS compatible spintronic devices based on a 2DHG., Comment: 6 figures

Silicon-based color-centers (SiCCs) have recently emerged as quantum-light sources that can be combined with telecom-range Si Photonics platforms. Unfortunately, using current SiCC fabrication, deterministic control over the vertical emitter position is impossible due to ion-implantation's stochastic nature. To overcome this bottleneck towards high-yield integration, we demonstrate a radically innovative creation method for various SiCCs, solely relying on epitaxial growth of Si and C-doped Si at atypically-low temperatures in a ultra-clean growth environment. These telecom emitters can be confined within sub-1nm thick layers embedded at arbitrary vertical positions within a highly crystalline Si matrix. Tuning growth conditions and doping, different SiCC types, e.g., W-centers, T-centers, G-centers, or derivatives like G'-centers can be created, which are particularly promising as Si-based single-photon sources and spin-photon interfaces. The zero-phonon emission from G'-centers can be conveniently tuned by the C-concentration, leading to a systematic wavelength shift and linewidth narrowing towards low emitter densities.

The bending of a nonconducting piezoelectric ZnO nanowire is simulated by finite element method calculations. The top part is bent by a lateral force, which could be applied by an atomic force microscope (AFM) tip. The generated electrical potential is 0.3 V. This relatively high signal is, however, difficult to measure, due to the low capacitance of the ZnO nanowire (4x10^{-5} pF) as compared to the capacitance of most preamplifiers (5 pF). A further problem arises from the semiconducting properties of experimentally fabricated ZnO nanowires which causes the disappearance of the voltage signal within picoseconds., Comment: submitted to Applied Physics Letters