Characterization of GaN/Si Using Capacitance Spectroscopies

2006 ◽  
Vol 955 ◽  
Author(s):  
Steven R. Smith ◽  
John C. Roberts ◽  
P. Rajagopal ◽  
J. W. Cook ◽  
E. L. Piner ◽  
...  
Keyword(s):  
Response Time ◽  
Uv Light ◽  
Negative Response ◽  
Optical Measurements ◽  
Bandgap Energy ◽  
Admittance Spectroscopy ◽  
Interesting Phenomenon ◽  
Si Substrates ◽  
Three Samples ◽  
Lower Temperature

ABSTRACTLayers of GaN deposited on Si substrates have been studied using Thermal Admittance Spectroscopy (TAS) and Optical Admittance Spectroscopy (OAS). Transparent front-side contacts were used to facilitate the optical measurements. Six specimens were cut from the same location in two different wafers, and three samples were randomly chosen from other growths. A shallow level at EC − 0.051 eV was found in all the specimens using TAS. In some specimens this peak was asymmetric, indicating more than one level near this energy. Deeper levels were also seen in the high-temperature portion of the spectra, but were poorly resolved in most specimens. Illuminating the specimen with UV light at 25 K resulted in the thermal position of the peak shifting to a lower temperature, and hence, the calculated energy, of the peak shifting lower. The amplitude of the peak also decreased. Transient OAS measurements revealed the interesting phenomenon of negative persistent photo conductance at room temperature in some of the specimens when the illumination photon energy was less than the bandgap. The negative response time was very short. At lower temperatures, below 100 K, the negative response diminished, but the response time was still short. At wavelengths above the bandgap energy, normal transient response was seen, with a longer time constant.

Low-Temperature Deposition and Characterization of AlxIn1-xN Thin Films

1996 ◽  
Vol 449 ◽  
Author(s):  
Guohua Qiu ◽  
J. O. Olowolafe ◽  
Tao Peng ◽  
K. M. Unruh ◽  
C. P. Swann ◽  
...  
Keyword(s):  
Room Temperature ◽  
Chemical Vapor ◽  
Optical Measurements ◽  
Bandgap Energy ◽  
Nitride Semiconductors ◽  
X Ray Diffraction ◽  
X Ray ◽  
Si Substrates ◽  
Temperature Deposition

ABSTRACTThin III-V nitride semiconductors fidms are commonly prepared using metalorganic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE). These methods often require high temperatures (800–1000°C) for the films to grow epitaxially. In the present work, we deposited AlxIn1-xN films on Si substrates by reactive magnetron sputttering method at low substrate temperature. The properties of the films have been studied by RBS, x-ray diffraction, and optical measurements. The AlxIn1-xN films deposited at room temperature were confirmed to be crystalline by x-ray diffraction. Band gap energies of our AlxIn1-xN alloys varies from 1.9 ev to 4.2 ev The bandgap energy vs. lattice constant curve was constructed and confirmed to bow downwards.

scholarly journals An Optical Fiber Sensor Based on La2O2S:Eu Scintillator for Detecting Ultraviolet Radiation in Real-Time

Sensors ◽  
2018 ◽  
Vol 18 (11) ◽  
pp. 3754 ◽  
Author(s):  
Yongji Yan ◽  
Xu Zhang ◽  
Haopeng Li ◽  
Yu Ma ◽  
Tianci Xie ◽  
...  
Keyword(s):  
Optical Fiber ◽  
Response Time ◽  
Electromagnetic Interference ◽  
Uv Light ◽  
Optical Fiber Sensor ◽  
Temperature Response ◽  
Superior Performance ◽  
Fiber Sensor ◽  
Uv Detectors

A novel ultraviolet (UV) optical fiber sensor (UVOFS) based on the scintillating material La2O2S:Eu has been designed, tested, and its performance compared with other scintillating materials and other conventional UV detectors. The UVOFS is based on PMMA (polymethyl methacrylate) optical fiber which includes a scintillating material. Scintillating materials provide a unique opportunity to measure UV light intensity even in the presence of strong electromagnetic interference. Five scintillating materials were compared in order to select the most appropriate one for the UVOFS. The characteristics of the sensor are reported, including a highly linear response to radiation intensity, reproducibility, temperature response, and response time (to pulsed light) based on emission from a UV source (UV fluorescence tube) centered on a wavelength of 308 nm. A direct comparison with the commercially available semiconductor-based UV sensor proves the UVOFS of this investigation shows superior performance in terms of accuracy, long-term reliability, response time and linearity.

Growth of Ga2O3 Nanowires by a Vapor Transport Method and their Optical Transmittance Spectra

2020 ◽  
Vol 38 ◽  
pp. 3-9
Author(s):  
Shunji Ozaki ◽  
Yuki Nakahata
Keyword(s):  
Optical Transmittance ◽  
Vapor Transport ◽  
Bandgap Energy ◽  
Transmittance Spectra ◽  
Si Substrates ◽  
Gallium Metal ◽  
Fused Quartz ◽  
Colored Product ◽  
Transport Method ◽  
Vapor Transport Method

Gallium oxide (Ga2O3) nanowires were grown on fused quartz and Si substrates by a vapor transport method of heating gallium metal at 750−1100 °C in a tube of the horizontal furnace. The obtained white colored product has shown to be the Ga2O3 nanowires with average diameters ranging from 30 to 80 nm. The optical transmittance spectra indicated that the bandgap energy of Ga2O3 nanowire increases as the diameter of nanowire decreases.

High-efficiency near-UV light-emitting diodes on Si substrates with InGaN/GaN/AlGaN/GaN multiple quantum wells

2020 ◽  
Vol 8 (3) ◽  
pp. 883-888 ◽  
Author(s):  
Yuan Li ◽  
Zhiheng Xing ◽  
Yulin Zheng ◽  
Xin Tang ◽  
Wentong Xie ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Quantum Efficiency ◽  
High Efficiency ◽  
Light Emitting Diodes ◽  
Uv Light ◽  
Multiple Quantum ◽  
High Quantum Efficiency ◽  
Light Emitting ◽  
Si Substrates

High quantum efficiency LEDs with InGaN/GaN/AlGaN/GaN MQWs have been demonstrated. The proposed GaN interlayer barrier can not only increase the concentration and the spatial overlap of carriers, but also improve the quality of the MQWs.

scholarly journals Enhanced Humidity Sensing Response of SnO2/Silicon Nanopillar Array by UV Irradiation

Sensors ◽  
2019 ◽  
Vol 19 (9) ◽  
pp. 2141 ◽  
Author(s):  
Wei Li ◽  
Linlin Wang ◽  
Yun Cai ◽  
Peifeng Pan ◽  
Jinze Li ◽  
...  
Keyword(s):  
Magnetron Sputtering ◽  
Response Time ◽  
Specific Surface ◽  
Uv Irradiation ◽  
Recovery Time ◽  
Room Temperature ◽  
Uv Light ◽  
Humidity Sensing ◽  
Potential Applications ◽  
Humidity Sensitivity

In this work, a silicon nanopillar array was created with nanosphere lithography. SnO2 film was deposited on this nanostructure by magnetron sputtering to form an SnO2/silicon nanopillar array sensor. The humidity sensitivity, response time, and recovery time were all measured at room temperature (25 °C) with UV or without UV irradiation. As a result, the humidity sensitivity properties were improved by enlarging the specific surface area with ordered nanopillars and irradiating with UV light. These results indicate that nanostructure sensors have potential applications in the field of sensors.

Electrical Characterization and Microstructures of Y2O3-Doped Bi4Ti3O12 Thin Films

2013 ◽  
Vol 591 ◽  
pp. 208-211
Author(s):  
Min Chen ◽  
J. Liu ◽  
X.A. Mei
Keyword(s):  
Thin Films ◽  
Electrical Characterization ◽  
Rf Magnetron Sputtering ◽  
Layered Perovskite ◽  
Random Orientation ◽  
Large Shift ◽  
Si Substrates ◽  
Layered Perovskite Structure ◽  
Lower Temperature ◽  
Curie Temperature Tc

Y2O3-doped bismuth titanate (Bi4-xYxTi3O12: BYT) and pure Bi4Ti3O12 (BIT) thin films with random orientation were fabricated on Pt/Ti/SiO2/Si substrates by rf magnetron sputtering technique. These samples had polycrystalline Bi-layered perovskite structure without preferred orientation, and consisted of well developed rod-like grains with random orientation. Y-doping into BIT caused a large shift of the Curie temperature ( TC ) from 675 °C to lower temperature and a improvement in dielectric property. The experimental results indicated that Y doping into BIT also result in a remarkable improvement in ferroelectric property. The Pr and the Ec values of the BYT film with x=0.75 were 28 μC/cm2 and 65 kV/cm, respectively.

Cytochemische Untersuchungen zur Reproduktion des Tabakmosaikvirus

1961 ◽  
Vol 16 (8) ◽  
pp. 520-538 ◽  
Author(s):  
Hendrik Zech
Keyword(s):  
Electric Fields ◽  
Uv Light ◽  
Refraction Index ◽  
Optical Measurements ◽  
Uv Spectrophotometry ◽  
X Rays ◽  
Optical Absorbance ◽  
Wide Range ◽  
Light Losses

Crystalline or paracrystalline tobacco mosaic virus (TMV) inclusions are known to be composed mainly of densely packed TMV-rods. These inclusions were studied in situ within infected tobacco leaf hair cells by scanning UV-microspectrophotometry. Comparative measurements in the macroand micro ranges of the instruments were carried out on purified TMV at low and high concentrations, on its separated and reconstituted RNA and protein parts and on isolated TMV-crystals, to permit the interpretation of the optical properties of TMV inclusions in situ. The optical absorbance of TMV in solution and in dried concentrates at room temperature could in part be attributed to distribution inhomogeneities caused by local particle aggregations being oriented to differing degrees. The resulting non-uniform electric fields around and within such unevenly distributed particle complexes caused local jumps of the refraction index and thereby unspecific light losses, chiefly through scattering. The apparent deviation from Beers law was found to be greatest at particle concentrations of 1 - 2 per cent. At higher concentrations the contribution of scatter to light losses was found to decrease again, probably because of increasing order of particles within the aggregates. On the other hand the specific absorbance of the chromophores of TMV over a wide range of concentration was not affected to a measurable degree by changing the distances between the rods. There was no indication that the charged groups of the RNA-cores within intact particles interacted with charged groups of other particles however great their proximity. The ribose phosphate backbone of the RNA strand, deeply embedded within the protein helix, may account for this phenomenon. However, isolated TMV-RNA reacted strongly to changes of the surrounding electric fields when concentrations were varied, and showed pronounced hypochromicity at higher concentrations and following prolonged irridation by x-rays and UV-light. RNA in dried and irradiated droplets was characterized by up to 55% lower extinction coefficients than freshly prepared RNA in solution. The hyprochromic effects caused by irradiation were shown to be almost, but not completely reversible. Hypochromicity increased towards the shorter wavelengths, diminishing the ratio E260/E280 from about 2.0 for diluted RNA to 1.4 for concentrated specimens. Mixing TMV-protein subunits with RNA before drying, leading to partial reconstitution of TMV particles, diminished the hypochromic effect resulting from irradiation of the concentrate. High UV-radiation doses applied to concentrated TMV solutions led to a marked splitting of RNA from protein, as revealed by UV-spectrophotometry of the supernatants and pellets of centrifuged irradiated specimens. Model measurements of intracellular and subsequently isolated TMV crystals combined with empirically derived parameters led to the construction of a correction curve, permitting interpretations of optical measurements on in situ TMV inclusion bodies.

scholarly journals A Water-Stable Organic-Inorganic Hybrid Perovskite for Solar Cells by Inorganic Passivation

Crystals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 83 ◽  
Author(s):  
Edward Guangqing Tai ◽  
Ryan Taoran Wang ◽  
Jason Yuanzhe Chen ◽  
Gu Xu
Keyword(s):  
Solar Cells ◽  
Uv Light ◽  
Perovskite Solar Cells ◽  
Transport Layer ◽  
Bandgap Energy ◽  
Lead Iodide ◽  
Perovskite Layer ◽  
Rapid Degradation ◽  
Inorganic Hybrid ◽  
Hybrid Perovskite

Organic-inorganic hybrid halide perovskite solar cells (PSCs) have been a trending topic in recent years. Significant progress has been made to increase their power conversion efficiency (PCE) to more than 20%. However, the poor stability of PSCs in both working and non-working conditions results in rapid degradation through multiple environmental erosions such as water, heat, and UV light. Attempts have been made to resolve the rapid-degradation problems, including formula changes, transport layer improvements, and encapsulations, but none of these have effectively resolved the dilemma. This paper reports our findings on adding inorganic films as surface-passivation layers on top of the hybrid perovskite materials, which not only enhance stability by eliminating weak sites but also prevent water penetration by using a water-stable layer. The surface-passivated hybrid perovskite layer indicates a slight increase of bandgap energy (Eg=1.76 eV), compared to the original methylammonium lead iodide (MAPbI3, Eg=1.61 eV) layer, allowing for more stable perovskite layer with a small sacrifice in the photoluminescence property, which represents a lower charge diffusion rate and higher bandgap energy. Our finding offers an alternative approach to resolving the low stability issue for PSC fabrication.

Synthesis and Characterization of Ce-Doped BZT Thin Films Deposited by a RF Magnetron Sputtering Method

2006 ◽  
Vol 321-323 ◽  
pp. 1336-1339
Author(s):  
Won Seok Choi ◽  
Young Park ◽  
Jin Hyo Boo ◽  
Junsin Yi ◽  
Byung You Hong
Keyword(s):  
Thin Films ◽  
Surface Roughness ◽  
Magnetron Sputtering ◽  
Rf Magnetron Sputtering ◽  
Film Deposition ◽  
Si Substrates ◽  
Structural And Electrical Properties ◽  
Ceramic Capacitor ◽  
Diffraction Patterns ◽  
Lower Temperature

We investigated the structural and electrical properties of the 0.5% Ce-doped Ba(ZrxTi1-x)O3 (BZT) thin films with a mole fraction of x=0.2 and a thickness of 150 nm for the MLCC (Multilayer Ceramic Capacitor) application. Ce-doped BZT films were prepared on Pt/Ti/SiO2/Si substrates by a RF magnetron sputtering system as a function of Ar/O2 ratio and substrate temperature. X-ray diffraction patterns were recorded for the samples deposited with three different substrate temperatures. The thickness and the surface roughness of the films deposited with different Ar/O2 ratios were measured. The oxygen gas, which was introduced during the film deposition, had an influence on the growth rate and the roughness of the film. The surface roughness and dielectric constant of the Ce-doped BZT film varied with Ar to O2 ratios (5:1, 2:1, and 1:1) from 1.21 nm to 2.33 nm and 84 to 149, respectively. The Ce-doped BZT film deposited at lower temperature has small leakage current and higher breakdown voltage.

Effect of Hydrogen Post-Annealing on Transparent Conductive ITO/Ga2O3 Bi-Layer Films for Deep Ultraviolet Light-Emitting Diodes

2015 ◽  
Vol 15 (10) ◽  
pp. 7777-7780 ◽  
Author(s):  
Kyeong Heon Kim ◽  
Su Jin Kim ◽  
Sang Young Park ◽  
Tae Geun Kim
Keyword(s):  
Light Emitting Diodes ◽  
Uv Light ◽  
Rf Magnetron Sputtering ◽  
Light Emitting ◽  
Post Annealing ◽  
Three Samples ◽  
Two Samples ◽  
Potential Applications ◽  
Different Temperatures ◽  
Uv Transmittance

The effect of hydrogen post-annealing on the electrical and optical properties of ITO/Ga2O3 bi-layer films, deposited by RF magnetron sputtering, is investigated for potential applications to transparent conductive electrodes of ultraviolet (UV) light-emitting diodes. Three samples—an as-deposited sample and two samples post-annealed in N2 gas and N2–H2 gas mixture—were prepared and annealed at different temperatures ranging from 100 °C to 500 °C for comparison. Among these samples, the sample annealed at 300 °C in a mixture of N2 and H2 gases shows the lowest sheet resistance of 301.3 Ω/□ and a high UV transmittance of 87.1% at 300 nm.

Sign in / Sign up

Export Citation Format

Share Document