Strain-Tuning of the Optical Properties of Semiconductor Nanomaterials by Integration onto Piezoelectric Actuators

The tailoring of the physical properties of semiconductor nanomaterials by strain has been gaining increasing attention over the last years for a wide range of applications such as electronics, optoelectronics and photonics. The ability to introduce deliberate strain fields with controlled magnitude and in a reversible manner is essential for fundamental studies of novel materials and may lead to the realization of advanced multi-functional devices. A prominent approach consists in the integration of active nanomaterials, in thin epitaxial films or embedded within carrier nanomembranes, onto Pb(Mg1/3Nb2/3)O3-PbTiO3-based piezoelectric actuators, which convert electrical signals into mechanical deformation (strain). In this review, we mainly focus on recent advances in strain-tunable properties of self-assembled InAs quantum dots embedded in semiconductor nanomembranes and photonic structures. Additionally, recent works on other nanomaterials like rare-earth and metal-ion doped thin films, graphene and MoS2 or WSe2 semiconductor two-dimensional materials are also reviewed. For the sake of completeness, a comprehensive comparison between different procedures employed throughout the literature to fabricate such hybrid piezoelectric-semiconductor devices is presented. Very recently, a novel class of micro-machined piezoelectric actuators have been demonstrated for a full control of in-plane stress fields in nanomembranes, which enables producing energy-tunable sources of polarization-entangled photons in arbitrary quantum dots. Future research directions and prospects are discussed.Comment: review manuscript, 78 pages, 27 figure

X-ray Diffraction vs. Photoluminescence of Semiconductor -Nanostructures

In thesis we have investigated InGaAs quantum-dots (QDs) embedded in a GaAs membrane, using x-ray diffraction photoluminescence measurements. The QDs can be used as single photon-sources but one problem is that they have, to some extent, “statistically” deviating properties after growth, resulting in “atom-like” energy levels which differ slightly from dot to dot. Hence, to overcome this problem, one can tune the emission properties using strain as a “tuning knob” for the energy levels. To get active and reproducible control on the strain state, the GaAs membrane is bonded onto a piezoelectric substrate. This configuration allows reversibly inducing strain by applying a voltage to the piezoelectric substrate, with the GaAs membrane on top following the deformation of the piezo actuator. The first aim of this work is to investigate how the strain is transferred from the piezo via different bonding layers to the GaAs and hence to the QDs. A second aim is to provide a reliable set of material parameters (optical deformation potentials) linking the mechanical and optical properties. This is done by comparing the strain in induced in the GaAs membrane, measured by X-ray diffraction, to the calculated strain form the changes of the optical emissions and optimizing the deformation potentials to reduce the differences between calculated and measured strain values.submitted by Dorian ZissUniversität Linz, Masterarbeit, 2017(VLID)238964

Direct-bandgap emission from hexagonal Ge and SiGe alloys

\u3cp\u3eSilicon crystallized in the usual cubic (diamond) lattice structure has dominated the electronics industry for more than half a century. However, cubic silicon (Si), germanium (Ge) and SiGe alloys are all indirect-bandgap semiconductors that cannot emit light efficiently. The goal \u3csup\u3e1\u3c/sup\u3e of achieving efficient light emission from group-IV materials in silicon technology has been elusive for decades \u3csup\u3e2–6\u3c/sup\u3e. Here we demonstrate efficient light emission from direct-bandgap hexagonal Ge and SiGe alloys. We measure a sub-nanosecond, temperature-insensitive radiative recombination lifetime and observe an emission yield similar to that of direct-bandgap group-III–V semiconductors. Moreover, we demonstrate that, by controlling the composition of the hexagonal SiGe alloy, the emission wavelength can be continuously tuned over a broad range, while preserving the direct bandgap. Our experimental findings are in excellent quantitative agreement with ab initio theory. Hexagonal SiGe embodies an ideal material system in which to combine electronic and optoelectronic functionalities on a single chip, opening the way towards integrated device concepts and information-processing technologies. \u3c/p\u3

Direct-bandgap emission from hexagonal Ge and SiGe alloys

Silicon crystallized in the usual cubic (diamond) lattice structure has dominated the electronics industry for more than half a century. However, cubic silicon (Si), germanium (Ge) and SiGe alloys are all indirect-bandgap semiconductors that cannot emit light efficiently. The goal of achieving efficient light emission from group-IV materials in silicon technology has been elusive for decades. Here we demonstrate efficient light emission from direct-bandgap hexagonal Ge and SiGe alloys. We measure a sub-nanosecond, temperature-insensitive radiative recombination lifetime and observe an emission yield similar to that of direct-bandgap group-III–V semiconductors. Moreover, we demonstrate that, by controlling the composition of the hexagonal SiGe alloy, the emission wavelength can be continuously tuned over a broad range, while preserving the direct bandgap. Our experimental findings are in excellent quantitative agreement with ab initio theory. Hexagonal SiGe embodies an ideal material system in which to combine electronic and optoelectronic functionalities on a single chip, opening the way towards integrated device concepts and information-processing technologies

Direct-bandgap emission from hexagonal Ge and SiGe alloys

Silicon crystallized in the usual cubic (diamond) lattice structure has dominated the electronics industry for more than half a century. However, cubic silicon (Si), germanium (Ge) and SiGe alloys are all indirect-bandgap semiconductors that cannot emit light efficiently. The goal 1 of achieving efficient light emission from group-IV materials in silicon technology has been elusive for decades 2–6. Here we demonstrate efficient light emission from direct-bandgap hexagonal Ge and SiGe alloys. We measure a sub-nanosecond, temperature-insensitive radiative recombination lifetime and observe an emission yield similar to that of direct-bandgap group-III–V semiconductors. Moreover, we demonstrate that, by controlling the composition of the hexagonal SiGe alloy, the emission wavelength can be continuously tuned over a broad range, while preserving the direct bandgap. Our experimental findings are in excellent quantitative agreement with ab initio theory. Hexagonal SiGe embodies an ideal material system in which to combine electronic and optoelectronic functionalities on a single chip, opening the way towards integrated device concepts and information-processing technologies

Supporting raw data files as presented in the paper: Direct Band Gap Emission from Hexagonal Ge and SiGe Alloys

Data sets and Python codes to generate figures from these data sets

Supporting raw data files as presented in the paper: Direct Band Gap Emission from Hexagonal Ge and SiGe Alloys

Data sets and Python codes to generate figures from these data sets