20 research outputs found
Nonlocal resistance and its fluctuations in microstructures of band-inverted HgTe/(Hg,Cd)Te quantum wells
We investigate experimentally transport in gated microsctructures containing
a band-inverted HgTe/Hg_{0.3}Cd_{0.7}Te quantum well. Measurements of nonlocal
resistances using many contacts prove that in the depletion regime the current
is carried by the edge channels, as expected for a two-dimensional topological
insulator. However, high and non-quantized values of channel resistances show
that the topological protection length (i.e. the distance on which the carriers
in helical edge channels propagate without backscattering) is much shorter than
the channel length, which is ~100 micrometers. The weak temperature dependence
of the resistance and the presence of temperature dependent reproducible
quasi-periodic resistance fluctuations can be qualitatively explained by the
presence of charge puddles in the well, to which the electrons from the edge
channels are tunnel-coupled.Comment: 8 pages, 4 figures, published versio
Zinc oxide for electronic, photovoltaic and optoelectronic applications
We demonstrate that the atomic layer deposition (ALD) technique has large potential to be widely used in a production of ZnO films for applications in electronic, photovoltaic (PV) and optoelectronic devices. Low growth temperature makes the ALD-grown ZnO films suitable for construction of various semiconductor/organic material hybrid structures. This opens possibilities of construction of novel devices based on very cheap organic materials. This includes organic light emitting diodes and PV cells of the third generation, as discussed in the present work
ZnO as a conductive layer prepared by ALD for solar cells based on n-CdS/n-CdTe/p-Cu₁.₈S heterostructure
ZnO films with high conductivity are obtained by atomic layer deposition for
application in solar cells based on n CdS/ n CdTe / p Cu₁.₈S heterostructure. The
parameters of solar cells with ZnO electrode are calculated from light and dark currentvoltage characteristics and compared with those obtained for structures with Mo contact.
The advantages of ZnO electrode are discussed
Electronic Properties of Stacked ZrO₂ Films Fabricated by Atomic Layer Deposition on 4H-SiC
The electronic properties of ZrO₂/SiO₂ stacked dielectric layers are reported as a function for temperature of the atomic layer deposition process. A dielectric layer has been characterized by C-V and I-V measurements of MIS structures. A strong dependence of κ value of ZrO₂ layer has been observed as a function of deposition temperature T. The values within the range of κ≈16-26 have been obtained. All measured stacked dielectric layers show an increase in dielectric breakdown voltage compared to simple SiO₂ dielectric by average factor of 1.7 and factor of 2 (21 MV/cm) for high-κ oxides deposited at low temperature (85°C)
Optical Characterization of ZnO Nanorods Grown by the Ultra-Fast and Low Temperature Hydrothermal Process
The results of photoluminescence investigations of zinc oxide nanorods are reported. These nanorods grown on undoped silicon substrates were obtained by low temperature and ultra-fast version of a microwave-assisted hydrothermal method. The photoluminescence investigations show very high quality of the obtained material. From photoluminescence studies we conclude the lack of carrier localization effects. The photoluminescence is dominated by band gap edge emission of bound excitonic (donor bound excitons) origin. Thus, the photoluminescence quenching observed at increased temperatures is associated with thermal ionization of shallow donors. From photoluminescence analysis (changes of photoluminescence line width) a strength of exciton-acoustic phonon coupling is evaluated
Optical and Structural Characterization of Zinc Oxide Nanostructures Obtained by Atomic Layer Deposition Method
Zinc oxide is a II-VI semiconductor material which is gaining increasing interest in various fields such as biology, medicine or electronics. This semiconductor reveals very special physical and chemical properties, which imply many applications including a transparent electrode in solar cells or LED diodes. Among many applications, ZnO is also a prospective material for sensor technology, where developed surface morphology is very advantageous. In this work we present ZnO nanowires growth using atomic layer deposition method. ZnO nanowires were obtained using controlled physical properties. As a substrate we used gallium arsenide with gold-gallium eutectic droplets prepared on the surface at high temperature. To obtain the eutectic solution there was put a gold thin film on GaAs through the sputtering and then we annealed the sample in a nitrogen gas flow. The so-prepared substrate was applied for growth of ZnO nanowires. We used deionized water and zinc chloride as oxygen and zinc precursors, respectively. The eutectic mixture serves as a catalyst for the ZnO nanowires growth. Au-Ga droplets flow on the front of ZnO nanowires. Scanning electron microscopy images show ZnO nanorods in a form of crystallites of up to 1 μm length and a 100 nm diameter. It is the first demonstration of the ZnO nanowires growth by atomic layer deposition using the vapour-liquid-solid approach
High Quality Gate Insulator/GaN Interface for Enhancement-Mode Field Effect Transistor
The capacitance-voltage measurements were applied for characterization of the semiconductor/dielectric interface of GaN MOS capacitors with and gate stacks. From the Terman method low density of interface traps at interface was calculated for as-deposited samples. Samples with gate stacks have higher density of interface traps as well as higher density of mobile charge and effective charge in the dielectric layers. High quality of interface shows applicability of as a gate dielectric in GaN MOSFET transistors
Barriers in Miniaturization of Electronic Devices and the Ways to Overcome Them - from a Planar to 3D Device Architecture
We witness a new revolution in electronic industry - a new generation of integrated circuits uses as a gate isolator . This high-k oxide was deposited by the atomic layer deposition technique. The atomic layer deposition, due to a high conformality of deposited films and low growth temperature, has a large potential to be widely used not only for the deposition of high-k oxides, but also of materials used in solar cells and semiconductor/organic material hybrid structures. This opens possibilities of construction of novel memory devices with 3D architecture, photovoltaic panels of the third generation and stable in time organic light emitting diodes as discussed in this work