B. Hahn

Bio: B. Hahn is an academic researcher from University of Regensburg. The author has contributed to research in topics: Metalorganic vapour phase epitaxy & Epitaxy. The author has an hindex of 8, co-authored 19 publications receiving 220 citations.

Transmission electron microscopy and reflected high‐energy electron‐diffraction investigation of plastic relaxation in doped and undoped ZnSe/GaAs(001)

Abstract: We report on reflected high‐energy electron‐diffraction and transmission electron microscopy plane‐view investigation of the dislocation structure in doped and undoped ZnSe/GaAs(001) grown by molecular‐beam epitaxy and metal‐organic vapor‐phase epitaxy. The thicknesses of the investigated layers vary between 60 and 900 nm. Several stages of dislocation formation are found which occur at distinct layer thicknesses. Frank partial dislocations (up to 500 nm), Shockley partial dislocations (between 130 and 400 nm) with a maximum density at 300 nm, and perfect 60° dislocations (above 300 nm) are observed in samples with perfectly smooth surface. The formation of Shockley partial dislocations is strongly anisotropic which might be due to the higher mobility of α‐type dislocations. An increased roughness of the growing surface yields a suppression of Shockley partial dislocations and an irregular dislocation network with dislocations inclined to the 〈110〉 directions. A regular dislocation network with straight dislocations is found in Cl‐doped samples.

Quasiphase matched second harmonic generation in ZnSe waveguide structures modulated by focused ion beam implantation

Abstract: Second harmonic generation is investigated in a ZnSe/ZnS0.22Se0.78 waveguide grown by metal organic vapor phase epitaxy on (001) GaAs substrate. Phase matching is achieved by a first order periodic modulation of the nonlinear susceptibility χ(2) within the waveguide structure. The modulation is generated by a focused ion beam implantation technique, resulting in a well confined damage of the crystalline structure. The observed phase matching wavelengths corresponding to various modulation periods between 1.6 and 1.9 μm agree with those predicted by calculations.

Green-light-emitting ZnSe nanowires fabricated via vapor phase growth

Abstract: Stoichiometric ZnSe nanowires have been synthesized through a vapor phase reaction of zinc and selenium powder on the (100) silicon substrate coated with a gold film of 2 nm in thickness. The microstructures and the chemical compositions of the as-grown nanowires have been investigated by means of electron microscopy, the energy dispersive spectroscopy, and Raman spectroscopy. The results reveal that the as-grown materials consist of ZnSe nanowires with diameters ranging from 5 to 50 nm. Photoluminescence of the sample demonstrates a strong green emission from room temperature down to 10 K. This is attributed to the recombination of electrons from conduction band to the medium deep Au acceptors.

Stark effect and polarizability in a single CdSe/ZnSe quantum dot

Abstract: The quantum-confined Stark effect in a single self-assembled CdSe/ZnSe quantum dot was studied by means of highly spatially resolved photoluminescence spectroscopy. A nanotechnological approach making use of a capacitor-like geometry enabled us to apply a well-defined lateral electric field on the quantum dots. Stark shifts of up to 1.1 meV were obtained, which can be well fitted by a purely quadratic dependence on an electric field. In quite good agreement with theoretical calculations, an exciton polarizability of 4.9×10−3 meV/(kV/cm)2 can be extracted, while the permanent dipole moment in the lateral direction is found to be negligible.