Scientific Highlights

The chamber geometry of a system for molecular beam epitaxy (MBE) is known to affect technical aspects such as the macroscopic deposition homogeneity across a wafer. However, for the microscopic mechanisms governing the growth of thin films on a planar substrate, the chamber geometry does not play...

A strong asset of bottom-up nanowires and related nanowire heterostructures is the enhanced surface strain relaxation that delays the onset of plastic relaxation. As a matter of fact, GaN nanowires essentially free of dislocations can be directly grown on technologically relevant substrates such as...

The monolithic integration of light emitters on Si remains an important technological challenge for the development of intra-chip optical connections, as well as inter-chip connections. In this context, GaAs nanowires grown on Si substrates offer great potential, but their effective use for Si...

AlN is the material of choice for optoelectronic devices working in the deep ultraviolet (UV) spectral range. However, the use of AlN in applications has been hampered by the lack of native substrates, resulting in high defect densities of AlN thin films. An attractive opportunity is offered by...

When III-V compound semiconductors are grown as nanowires instead of planar thin films, crystal structures may form that otherwise would only be metastable. In consequence, changes in crystal structure can occur along the growth axis. This polytypism offers the chance to study the properties of...

One of the most demanding challenges for materials synthesis is the fabrication of nanostructures that enable the observation of quantum phase coherence phenomena. A prominent example is the excitonic Aharonov-Bohm effect, which requires nanoscale semiconductor rings with the highest structural...

GaN-based nanowires have emerged as a promising approach to light emission and solar energy harvesting applications. In this framework, p-type doping of GaN by Mg is one of the most important prerequisites for the fabrication of such devices. However, characterizing the electrical properties of...

The linear optical response of a bulk material is fully described by the wavelength-dependent complex refractive index n(λ). However, if the material is structured on a scale comparable to or smaller than the wavelength of the light it interacts with, the optical response is additionally affected or...

Heterostructures formed within nanowires offer the key advantage that misfit strain can relax at the nanowire sidewalls and partition throughout the entire nanostructure. As a result, using nanowires as nanoscale substrates enables the realization of coherent heterostructures well beyond the...

(In,Ga)N/GaN nanowire ensembles with a tunable bandgap from the UV to the infrared are very promising building blocks for solid–state lighting, photovoltaics and solar to fuel energy converters. The direct integration of such nanostructures on bendable metal foils would open the path to the...

The possibility to tune the bandgap of (In,Ga)N across the whole visible spectral range makes this alloy attractive for solar harvesting applications. Enhanced light conversion efficiencies are expected when (In,Ga)N is grown in the form of nanowires, since the nanowire geometry allows strain...

The realization of semiconductor structures with stable excitons at room temperature is crucial for room temperature optoelectronic applications involving excitons. Quantum confinement has commonly been employed for enhancing excitonic effects in semiconductor heterostructures. Dielectric...

Low-dimensional semiconductor nanostructures have attracted a lot of interest in the past decades, largely due to their applications in low-energy consumption and energy-harvesting devices. Owing to surface effects, the performance of such devices strongly depends on the nanocrystal morphology. To...

The bottom-up growth of free-standing nanowires has opened up new opportunities for the epitaxial combination of dissimilar materials, because strain induced by mismatch in lattice constants can elastically relax at the free nanowire sidewalls. Here, we take the level of dissimilarity between...

Line-of-sight quadrupole mass spectrometry (QMS) is a unique non-destructive technique that enables the measurement of the desorption of adatoms during the growth of films as well as nanostructures in a high-vacuum environment. In this work, we use QMS to investigate the temporal evolution of GaN...

Hydrogen is a clean, storable energy carrier. However, nowadays most hydrogen is produced from fossil resources under emission of CO2. From an environmental point of view, the most attractive method to produce hydrogen is the direct conversion of water into hydrogen and oxygen employing sunlight,...

GaN nanowires (NWs) have attracted great interest for the fabrication of nanoscale devices such as light emitting diodes, bio-sensors, and photovoltaic cells because they exhibit a high crystal quality independent of the substrate used for growth. However, despite the potential of these...

With the ability to synthesize semiconductors in high crystal quality on foreign substrates, nanowires (NWs) offer new and promising possibilities for the future miniaturization of optoelectronic devices and their integration with Si technology. The bottom-up fabrication of NW-based light emitting...

So far, the use of Si as n-type dopant for GaAs nanowires has been hampered by its amphoteric behavior that leads to heavy charge-carrier compensation. We demonstrate how the doping amphotericity of Si is related to the growth mode and the growth kinetics, and how it can be controlled in favor of...

The spontaneous polarization is a fundamental property of wurtzite semiconductors or any other pyroelectric crystal. It results in electric fields in semiconductor heterostructures affecting the design of devices for solid-state lighting or power electronics. However, this quantity is difficult to...

GaN nanowires (NWs) can be synthesized in high structural quality even on foreign substrates, in contrast to conventional heteroepitaxial GaN films. This may result in cost-efficient implementations for opto-electronic applications. Most of these applications require a large number of NWs, i.e., NW...

The equilibrium modification of bulk III-As semiconductors is the zincblende (ZB) phase. However, these materials crystallize partially or even predominantly in the wurtzite (WZ) structure when grown in the nanowire form. In particular, GaAs nanowires often exhibit a mixed crystal structure with ZB...