V. Khorenko

Composition control in metal-organic vapor-phase epitaxy grown InGaAs nanowhiskers

InGaAs nanowhiskers were grown by metal-organic vapor-phase epitaxy on (111)B GaAs substrates using the vapor-liquid-solid growth mode. The diameter of nanowhiskers was defined by monodisperse gold nanoparticles deposited on the GaAs substrate from the liquid phase. By adjusting the triethylgallium to trimethylindium flow ratio, InxGa1−xAs whiskers with various compositions were realized. The composition characterization of the grown whiskers was done by high-resolution x-ray diffractometry. A detailed analysis of measured spectra allowed resolving the presence of an InGaAs three-dimensional layer between whiskers. High-resolution transmission electron microscopy investigation revealed the lattice constant of the grown whisker structures, which agrees with the whisker composition defined by x-ray diffractometry. Finally, low-temperature photoluminescence measurements of the realized InGaAs whiskers were carried out.

Photoluminescence of GaAs nanowhiskers grown on Si substrate

GaAs nanowhiskers were grown by metalorganic vapor-phase epitaxy on (111) Si substrates using the vapor-liquid-solid growth mode. The diameter of the nanowhiskers was defined by polydisperse catalytic Au nanoparticles in the range from 5 to 100 nm deposited on the Si substrate from the liquid phase. The low-temperature photoluminescence spectra exhibit a series of unresolved exciton-related transitions shifted to a shorter wavelength due to the quantization effects. Despite some structure defects, relatively high photoluminescence intensity and its linear dependence on the excitation power without saturation confirms the good material quality of fabricated GaAs nanowhiskers.

Gaas whiskers grown by metal-organic vapor-phase epitaxy using Fe nanoparticles

GaAs nanowhiskers were grown by metal-organic vapor-phase epitaxy on (111)B GaAs substrates. The diameter of the nanowhiskers was defined by monodisperse Fe nanoparticles deposited on the GaAs substrate from the vapor phase. The growth temperature of the whiskers was investigated from 480to520°C. The whiskers are preferentially directed along the crystal orientations of ⟨001⟩, ⟨111⟩, and their equivalents. High-resolution transmission electron microscopy characterization including energy disperse x-ray spectroscopy measurements revealed not only iron oxide but also arsenic inside the seed particle at the top of the GaAs whiskers. This indicates that the particle stays at the top during the whisker growth.

A Four-Resonant-Tunneling-Diode (4RTD) NAND/NOR Logic Gate

A NAND/NOR logic gate using four resonant-tunneling diodes (RTDs), which is introduced by the analogy of RTD current-voltage characteristics to those of superconducting Josephson junctions (JJs), has been investigated. The NAND/NOR function is obtained by a simple configuration consisting of four RTDs without using any conventional transistors, such as HEMTs or HBTs. The operation principle is analyzed by a graphical method, and a condition required for a normal logic operation is clarified. A NAND/NOR circuit was fabricated by using an InP technology. The experimental result agrees well with our circuit simulation

Single InGaAs nanowhiskers characterized by analytical transmission electron microscopy

Single crystal In x Ga1−x As nanowhisker were grown by metal-organic vapour-phase epitaxy on (111)B GaAs substrates using the vapour–liquid–solid growth mode. Present study is aimed to the direct evaluation of the lattice parameter, the phase, and the composition of nanowhiskers with high spatial resolution by high-resolution transmission electron microscopy and analytical transmission electron microscopy including energy-dispersive X-ray spectroscopy in nano probe mode. The goal is the direct identification of the quantified concentrations and the local element distributions at characteristic whisker areas. In particular, chemical measurements provide insights into the segregation of the gallium and arsenic out of the gold seed particle and the presence of indium remaining in the Au particle of the as-prepared whiskers. For comparison, InGaAs nanowhiskers are characterized by high-resolution X-ray diffractometry providing the mean whisker composition information indirectly by substituting the X-ray data into the formula of the law of Vegard.

Characterisation of GaAs nanowhiskers grown on GaAs and Si substrates

We report the growth of GaAs nanowhiskers on GaAs and Si substrates using two alternative Ga-precursors and demonstrate results of photoluminescence and electrical characterisation of the grown structures towards the fabrication of III/V nanoscaled optoelectronic devices on Si substrate.

Design and modelling of a III/V mobile-gate with optical input on a silicon substrate

The co-integration of III/V devices such as InGaAsP PIN diode and an (In)AlAs/In(Ga)As Resonant Tunnelling Diodes with state-of-the-art silicon NMOS transistors is studied. The III/V devices layers are epitaxially grown and fabricated on silicon substrates for the extraction of model parameters. The performance of a potentially low-cost optical receiver circuit on silicon is simulated using HSPICE up to 10 Gb/s.

Buffer optimization for InP-on-Si [001] quasi-substrates

Different types of InGaAs/InP(InAlAs) superlattice structures and low temperature grown single InAlAs layers are examined with respect to the defect reduction and improvement of the surface roughness of InP-on-Si [001] quasi-substrates. By using an InAlAs layer grown at optimized conditions a surface roughness of 1.9 nm and a good crystal quality are achieved. Resonant-tunneling diodes fabricated on top of the improved quasi-substrate exhibit a peak-to-valley-ratio of 2 and a peak current density of 27 kA/cm at room temperature showing the high application potential of this approach.

Fabrication and Electrical Characterisation of n-InAs Single Nanowhisker Field-Effect Transistors

We fabricated and characterised an n-InAs nanowhisker field effect transistors. Nanowhiskers were grown by metal-organic vapour-phase epitaxy (MOVPE) using the vapour-liquid-solid (VLS) growth mode. The fabricated device exhibits a high normalized transconductance (gm /wg) of 895 mS/mm and electron mobility above 4800 cm 2/Vs