Fabrication method of high-quality Ge nanocrystals on patterned Si substrates by local melting point control.

The local melting point of a Ge thin film can be controlled by a hole-array pattern on the host Si substrate due to the variations in the stress distribution and the surface morphology induced by the pattern. A simple annealing process is developed from this effect to produce Ge NCs with a single-domain-crystal size over 20 nm, confirmed by transmission electron microscopy and Raman spectroscopy, from an electron-gun-evaporated Ge thin film on the patterned Si substrate. The effect of the dimensions of the hole array is also investigated. Photoluminescence observed around 1157 nm from some of the samples shows the possibility of improving the infrared emission capability by this proposed method.

Correlated electric fluctuations in GaN nanowire devices.

We report an experimental study on the correlation spectrums between different sections of a multi-contact GaN nanowire device. Our results indicate that there exists a negative correlation between the voltage fluctuations of adjacent sections of the nanowire separated by a metal contact in the transition region between the low-frequency 1/f noise and the high-frequency white thermal noise. We suggest that this correlation is caused by the voltage fluctuation under the contact area.

Mobility asymmetry in InGaAs/InAlAs heterostructures with InAs quantum wires.

Strong asymmetry of electron mobility in InGaAs/InAlAs heterostructures (lattice matched to InP) with the presence of InAs quantum wires was observed. Self-assembled InAs quantum wires, embedded in an InGaAs matrix close to the hetero-interface, has a strong effect in electron conduction in the interface channel. The low temperature mobility for electrons moving parallel to the quantum wires is much higher than that of electrons moving perpendicular to the wires. The asymmetry in mobility is attributed to the difference in scattering cross section of the quantum wires in these two directions.