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In this Letter, the p-GaN high electron mobility transistor (HEMT) with hybrid drain of recessed Schottky (RS) and p-GaN isolation blocks' drain (HSP drain) is proposed and fabricated for good reverse blocking capability. The related operation mechanism has been investigated and revealed. The proposed device features a drain terminal consisting of the array-distributed recessed Schottky and p-GaN isolation blocks. Based on the features, the reverse leakage current (5 × 10−9 A/mm at VDS = −100 V) is obviously reduced by two orders of magnitude compared with that (5 × 10−7 A/mm) of p-GaN HEMTs only with recessed Schottky (RS) drain, which is the lowest leakage current among the reported GaN-on-Si reverse blocking transistors. The introduction of these p-GaN isolation blocks has a negligible impact on Von (Von = 0.63 V). Therefore, a good improvement in the trade-off between the reverse leakage current and Von could be achieved because of the significant reduction in the reverse leakage current without sacrificing Von. In addition, the reverse breakdown voltage of −800 V at 1 μA/mm with a substrate grounded in the proposed device is evidently improved compared with the counterpart (−680 V), which is attributed to effective alleviation of the high electric field near the HSP drain. These results demonstrate the significance and potential of p-GaN HEMTs with HSP drain in reverse blocking applications.

A Schottky np diode (SNPD) was fabricated on a 4H-SiC C-face epitaxial wafer, and its I-V characteristics were investigated. The diode showed a high blocking voltage of 300 V and ultralow on-resistance of 0.18 m Ω cm2 at a forward bias of 2.4 V. This value is almost the same as the resistance of the 4H-SiC bulk substrate, indicating that the resistance of the drift layer is almost zero and does not contribute to the observed on-resistance. As the temperature was increased, the forward I-V curve moved in parallel as the built-in bias shifted to a lower voltage due to the reduction in the barrier height of the np junction. This means that the resistance of SNPD above built-in bias is the same regardless of temperature. These results suggest that the diode is different from the conventional Schottky diodes and pn diodes. This diode has great potential for devices with both ultralow on-resistance and high blocking voltage.

A magnetic random access memory cell architecture is fabricated where the pinned layer is reversed by heating above a reduced blocking temperature with a current pulse crossing the junction, and cooled under an external applied field (word line), minimizing half-select switching of nonaddressed bits. In order to improve Joule heating and increase breakdown voltage, a double barrier structure was used, with a common antiferromagnetic layer (60 A MnIr) two pinned 30 A CoFe layers, and two free layers incorporating nanooxide structures. The blocking temperature was reduced to 120 °C. A TMR of 25% was achieved for both single barrier and double barrier tunnel junctions with resistance×area products of ∼40 Ω×μm2 and ∼280 Ω×μm2, respectively. Pinned layer writing allows the definition of a three-state memory, requiring, however, a destructive read out. A significant improvement of writing efficiency is observed with the double barrier structure. A 10 ns current pulse of 9 mA/μm2 is sufficient to heat the double...

We report the performance of a 30 period p-GaAs/AlxGa1−xAs heterojunction photovoltaic infrared detector, with graded barriers, operating in the 2–6 μm wavelength range. Implementation of a current blocking barrier increases the specific detectivity (D*) under dark conditions by two orders of magnitude to ∼1.9 × 1011 Jones at 2.7 μm, at 77 K. Furthermore, at zero bias, the resistance-area product (R0A) attains a value of ∼7.2 × 108 Ω cm2, a five orders enhancement due to the current blocking barrier, with the responsivity reduced by only a factor of ∼1.5.

In this letter, we demonstrate the use of very high performance, ultrahigh impedance, electric potential probes in the detection of electrical activity in the brain. We show that these sensors, requiring no electrical or physical contact with the body, can be used to monitor the human electroencephalogram (EEG) revealing, as examples, the α and β rhythms and the α blocking phenomenon. We suggest that the advantages offered by these sensors compared with the currently used contact (Ag/AgCl) electrodes may act to stimulate new developments in multichannel EEG monitoring and in real-time electrical imaging of the brain.

We report the improvement of quantum cascade lasers emitting at λ∼5 μm by introducing AlAs blocking barriers together with strain-compensating InAs layers into the active regions. The blocking barriers are designed to selectively prevent electrons in the initial laser state from tunneling out of the active region, while maintaining the high tunneling probabilities of the electrons in the final laser states. Adopting blocking barriers, the maximum peak power per facet at 77 K (300 K) is increased from 285 (30 mW) to 900 mW (240 mW), and the maximum operation temperature in pulsed mode has been improved from 320 to 350 K with respect to a reference sample without blocking barriers.

Ten-stacked InAs/GaAs quantum-dot infrared photodetectors with single Al0.3Ga0.7As blocking layers at either side of the stacked dots are investigated. With peak responsivity 214 mA/W and specific detectivity 1.17×1010 cm Hz1/2/W at 6 μm, quantum-dot infrared photodetectors with single-sided blocking layers are superior in responsivity with compatible detectivity as compared to those without blocking layers. Enhancement of the photoelectron avalanche process and the absence of negative differential conductance are observed. The devices exhibit two different infrared absorption regions at 2–6 and 6–10 μm, which indicates a wide detection window of the device.

In an attempt to suppress the dark current, the barrier layer engineer for solution-processed PbSe colloidal quantum-dot (CQD) photodetectors has been investigated in the present study. It was found that the dark current can be significantly suppressed by implementing two types of carrier blocking layers, namely, hole blocking layer and electron blocking layer, sandwiched in between two active PbSe CQD layers. Meanwhile no adverse impact has been observed for the photo current. Our study suggests that this improvement resides on the transport pathway created via carrier recombination at intermediate layer, which provides wide implications for the suppression of dark current for infrared photodetectors.

We present a 3×3 surface‐normal wavelength‐selective crossbar using polymer‐based volume holograms. A prototype device is demonstrated using the center wavelength of 775 nm and Δλ=10 nm. Employment of 1/4‐pitch graded‐index rod lenses reduces the required nine wavelengths to three while maintaining the 3×3 interconnects. The diffraction efficiencies of 75%, 83%, and 75% are experimentally confirmed for wavelength 765, 775, and 785 nm, respectively. Surface‐normal configuration eliminates the conventional edge‐coupling scheme which is vulnerable in a harsh environment. A 3×3 crossbar is demonstrated with a two‐way system insertion loss less than 3 dB and channel‐to‐channel cross talk less than 20 dB.

Efficient carrier blocking by a single ‘‘attractive’’ potential is demonstrated using a strained Si0.85Ge0.15/Si quantum well (QW). The carrier blocking becomes pronounced at increased temperatures as most of the carriers at the QW bound state are thermalized with the barrier band edge. The carrier blocking efficiency at 100 K is almost of the order of unity as compared to insufficient carrier blocking due to a large ‘‘repulsive’’ potential associated with SiO2. The carrier blocking arises from efficient hole reemission from the QW that reflects a highly efficient carrier capture to the strained Si1−xGex/Si QWs from Si barriers. It is further shown that a single QW is the optimized geometry for efficient carrier blocking and that multiple well potentials lead only to a reduced blocking efficiency.

An experimental investigation was made on the use of a PtSi Schottky barrier for blocking injected electron dark current in a back‐illuminated impurity‐band‐conduction (IBC) photodetector, a device used for detecting long‐wavelength infrared (LWIR) radiation. Measured results on the Schottky barrier height as well as current versus applied bias results are presented, and show that the desired blocking capability has been attained. At the low operating temperatures (∼10 K) of the IBC device, the injected dark current is below our measurement capability for applied biases of up to 10 V. Injected dark current in conventional devices occurs at biases of ∼1 V. The modified device configuration discussed here would enable one to store the mobile ionized donor charge for subsequent readout.

Four n‐i‐n GaAs/AlGaAs diodes have been used to demonstrate that at room temperature the carrier blocking is influenced by the X‐valley superlattice in a multiquantum barrier. The diode with a Γ‐X crossover multiquantum barrier has a current at least three orders lower than the corresponding diode with only a bulk barrier. However, diodes without Γ‐X crossover barriers have resistance as low as 10 Ω in spite of whether a multiquantum barrier exists or not. This indicates that the X‐valley superlattice plays an important role in blocking the current flowing across/through a multiquantum barrier.

A system of generating and receiving orbital angular momentum (OAM) radio beams, which are collectively formed by two circular array antennas (CAAs) and effectively optimized by two intensity controlled masks, is proposed and experimentally investigated. The scheme is effective in blocking of the unwanted OAM modes and enhancing the power of received radio signals, which results in the capacity gain of system and extended transmission distance of the OAM radio beams. The operation principle of the intensity controlled masks, which can be regarded as both collimator and filter, is feasible and simple to realize. Numerical simulations of intensity and phase distributions at each key cross-sectional plane of the radio beams demonstrate the collimated results. The experimental results match well with the theoretical analysis and the receive distance of the OAM radio beam at radio frequency (RF) 20 GHz is extended up to 200 times of the wavelength of the RF signals, the measured distance is 5 times of the original measured distance. The presented proof-of-concept experiment demonstrates the feasibility of the system.

We compare the gain in power conversion efficiency (PCE) achieved by inserting either amorphous or crystalline exciton blocking layers at the anode interface for planar (PHJ) and planar-mixed heterojunction (PM-HJ) organic solar cells based on Tetraphenyldibenzoperiflanthene and fullerenes. For PHJ devices, there is a gain of more than 37% for both types of blocking layers, mainly due to an increase in photocurrent, indicating that this gain can be solely ascribed to the exciton blocking effect. A templating effect as proposed in literature for crystalline blocking layers cannot be affirmed. On the contrary, it is shown that there is a connection between the choice of acceptor (C60/C70) and the blocking effect on the anode side. Moreover, we can show that also for PM-HJ devices a remarkable efficiency enhancement is possible. The insertion of suitable blocking layers at the anode interface can alter the effective work function and thus the open-circuit voltage, leading to a maximum PCE of 5.8% in single junction cells.

The effect of different Al(Ga)N electron blocking heterostructures (EBH) on the emission spectra and light output power of 290 nm light emitting diodes (LEDs) has been investigated. The carrier injection and internal quantum efficiency of the LEDs is simulated and compared to electroluminescence measurements. The highest light output power has been found for LEDs with an Mg-doped AlN/Al0.7Ga0.3N EBH with an AlN layer thickness >3 nm. The output power of these LEDs was 8.5-times higher compared to LEDs without EBH. This effect is attributed to an improved carrier injection and confinement which prevents electron leakage into the p-doped region of the LED with a simultaneously enhanced hole injection into the active region.

Conventional means of attenuating airborne sound usually require blocking the air medium with a solid material. By exploiting properties of membrane-type acoustic metamaterials (MAMs), we demonstrate large transmission loss to be achievable across a sizable orifice through which air can freely flow. We find that interaction of resonating field of the MAMs with the continuous sound field passing through the orifice is responsible for such phenomenon. The narrow-band characteristic of this effect can be used for acoustic filtering of noise with a particular narrow frequency band.

The present disclosure relates to photosensitive optoelectronic devices comprising a compound blocking layer located between an acceptor material and a cathode, the compound blocking layer comprising: at least one electron conducting material, and at least one wide- gap electron conducting exciton blocking layer. For example, 3,4,9, 10 perylenetetracarboxylic bisbenzimidazole (PTCBI) and 1,4,5, 8-napthalene-tetracarboxylic- dianhydride (NTCDA) function as electron conducting and exciton blocking layers when interposed between the acceptor layer and cathode. Both materials serve as efficient electron conductors, leading to a fill factor as high as 0.70. By using an NTCDA/PTCBI compound blocking layer structure increased power conversion efficiency is achieved, compared to an analogous device using a conventional blocking layers shown to conduct electrons via damage-induced midgap states.

P-type AlGaN/GaN/InGaN superlattices were incorporated in a InGaN based blue light emitting diode as electron blocking layer to minimize the temperature dependence on optical output power. For the characteristic temperatures in range of 10 to 100 °C and at operation current of 350 mA, the external quantum efficiency varied by less than 0.5%. For the presented device, the negative characteristic temperature was shown to occur below temperature of 50 °C. The improved temperature stability in optical output power is thought to be attributed to (1) the efficiency of hole carrier transport in AlGaN/GaN/InGaN superlattices and (2) the enhanced blocking of electron overflow between multiple quantum wells and AlGaN/GaN/InGaN superlattices.

High efficiency blue phosphorescent organic light emitting diodes have been developed by using a simple device structure. A derivative of spirobifluorene based phosphine oxide was used both as a host and an electron transport layer with an exciton blocking function. A maximum quantum efficiency of 19.2% and a current efficiency of 37.2cd∕A were obtained by using a simple device structure without a hole blocking layer.

Charge-trapping type flash memory devices with various integrations of metal gates having different work functions and blocking oxides were investigated in this work. Improved erasing speed together with acceptable reliability characteristics can be achieved by the integration of high work-function metal gate and high-k blocking oxide due to an efficient suppression of electron back tunneling through the blocking oxide during erasing operation for the MoN sample. Specifically, the high work-function value of MoN metal gate can be kept only by integrating with the Al2O3 blocking oxide because it can suppress the formation of molybdenum-silicide. Moreover, high-speed erasing can also be demonstrated by combining the MoN metal gate with an HfAlO charge trapping layer when band-to-band hot hole erasing method is adopted.

We demonstrate that a negative feedback between vapor pressure and condensation rate may be established in two-phase systems during vapor compression with rates of practical importance. As a result, dynamic condensation blocking occurs. The effect is studied numerically in the case of filling a no-vent insulated tank by liquid hydrogen. It is shown that the filling dynamics quite sensitively depends on the filling rate, and for sufficiently fast filling rates consist of a fast stage dominated by gas compression and a slow stage governed by heat conduction in the liquid.

One important parameter that quantifies the performance of ferromagnetic shape memory alloys is the blocking stress. To date, the low blocking levels (

GaN∕AlxGa1−xN superlattices (SLs) with different period thicknesses tp were grown as interlayers between GaN and AlyGa1−yN epilayers. The effect of threading dislocations (TDs) blocking became more evident with increasing tp. Transmission electron microscopy analysis shows that TDs are inclined to be bended in SLs and terminated in GaN wells as a result of strain. X-ray diffraction measurement also validated that GaN wells played a more important role as a TDs filter. The blocking of TDs in SLs resulted in an abnormal decrease in relaxation factors R(SLs) with increasing tp.

A distributed charge storage with Ni nanocrystals embedded in the SiO2 and HfO2 layer has been fabricated in this study. The mean size and aerial density of the Ni nanocrystals are estimated to be about 5nm and 3.9×1012∕cm2, respectively. The nonvolatile memory device with Ni nanocrystals exhibits 1V threshold voltage shift under 4V write operation. The device has a long retention time with a small charge lose rate. Besides, the endurance of the memory device is not degraded up to 106 write/erase cycles.

In this letter, the Co nanocrystals using SiO2 and HfO2 as the tunneling and the control dielectric with memory effect has been fabricated. A significant memory effect was observed through the electrical measurements. Under the low voltage operation of 5V, the memory window was estimated to ∼1V. The retention characteristics were tested to be robust. Also, the endurance of the memory device was not degraded up to 106 write/erase cycles. The processing of the structure is compatible with the current manufacturing technology of semiconductor industry.

Enhanced electroluminescent efficiency using a deoxyribonucleic acid (DNA) complex as an electron blocking (EB) material has been demonstrated in both green- and blue-emitting organic light-emitting diodes (OLEDs). The resulting so-called BioLEDs showed a maximum luminous efficiency of 8.2 and 0.8cd∕A, respectively. The DNA-based BioLEDs were as much as 10× more efficient and 30× brighter than their OLED counterparts.

Numerical modeling demonstrates an alternate bias mode for blocked impurity band (BIB) detectors that can reduce growth constraints on the high purity blocking layer. Initiating depletion from the contact on the active layer (the opposite of conventional operation) significantly reduces the large electric field and resultant voltage drop in the blocking layer. Electric field profiles are presented to show that the alternate bias allows for growth of significantly thicker blocking layers. This could be applied to produce modified BIB devices in far-infrared materials (λ>40μm) where growth issues associated with the blocking layer have prohibited conventional operation.

Magnetic properties of the Sr-doped BaCoO$_3$ are explained on the basis of ab initio calculations and the analysis of experimental literature. Formation of magnetic clusters bigger than in the parent compound and increase in the blocking temperature are observed. Superparamagnetism remains at room temperature. The possibility of tuning the size and properties of the magnetic clusters with doping is explored., 3 pages, 1 figure

We present a device structure of SiO2∕SiN∕Al2O3 (SANOS). The use of a high-k dielectric material, specially Al2O3, in the blocking oxide concentrates the electric fields across the tunnel oxide and SiN, and releases it across the blocking oxide under program and erase mode. This effect leads to lower program and erase voltage as well as faster erase speed than the conventional SiO2∕SiN∕SiO2 (SONOS) device. Moreover, it is shown that the fast erase operation is performed even at a thicker tunnel oxide over 30A where the hole direct tunneling current through the tunnel oxide is reduced significantly and thus the SANOS device has the excellent bake retention.

The distribution of local blocking temperatures (TBi) in an exchange-coupled half-metallic-Fe3O4–antiferromagnetic-Cr45.5Mn45.5Pt9 system (in atomic %) was investigated, with the aim of confirming thermal stability of unidirectional anisotropy induced in Fe3O4 film, which has hard magnetic properties. The distribution of TBi was mostly at or around 265°C. This distribution in the Fe3O4–CrMnPt system was equivalent or superior to that found in a previously studied soft magnetic-Ni81Fe19–antiferromagnetic-Pt50Mn50 system, where PtMn had been used in a giant magnetoresistance device as the standard antiferromagnetic material for the exchange-biased layer. These results make it reasonable to conclude that the exchange coupled Fe3O4–CrMnPt system has excellent thermal stability.

Heterobarrier blocking structure InGaAlP visible light laser diodes employing a thin active layer (0.04 μm) and asymmetry coatings have been fabricated. The high light‐output power operation with this heterobarrier blocking structure was investigated. The light‐output power versus cw current curve was linear up to 43 mW and a maximum light output power of 51 mW was obtained. A high‐power operation such as 20 mW was maintained at 40 °C. Stable oscillation in the fundamental transverse mode was obtained up to 30 mW. These results show that this heterobarrier blocking structure supplies a sufficient current confinement effect even under a high‐light output power operation.

The fabrication and performance of high‐speed and high‐power 1.3‐μm InGaAsP buried crescent lasers with semi‐insulating current blocking layers are reported. A modulation bandwidth of 11 GHz and acw output power of 42 mW/facet have been achieved. An approximate circuit model of the semi‐insulating buried crescent laser, which describes the effect of dc bias on parasitic capacitance at high‐speed operation, is also presented.

Graphical solutions and experimental results of the blocking oscillation of the guided‐wave optical bistable devices using dc drift phenomena of LiNbO3 are reported. The frequency of the oscillation can be varied in the range from 0.1 to 100 Hz by changing biasing voltage and input light level.

The process by which threading dislocations present in the substrate are bent into the interface plane during epitaxial layer growth and thus are blocked from propagating into the epitaxial layer has been observed in growth of the II‐VI ternary alloy Hg1−xCdxTe on CdTe and Cd1−zZnzTe substrates. Stereo‐pair transmission electron micrographs were analyzed which clearly revealed the interfacial dislocations to be in a planar network, as has been previously reported for III‐V epitaxial systems in which the blocking mechanism has been identified by other investigators. Additional evidence of the blocking phenomenon has been provided by chemical dislocation‐revealing etching, which verified that the substrate dislocations were not present in the layer.

The operation of an image storage panel, which is read in by means of optical absorption and read out in visible light by means of the Pockels electro‐optic effect, has been demonstrated. The sensing, storing, and readout medium consists of a single‐crystal film of cubic ZnS coated with a blocking contact. Performance characteristics observed to date on devices with areas between 1 and 2 cm2 are resolution of 85 line pairs/mm, continuous visible readout for 1 h, and image storage for up to 100 h. The readin sensitivity to achieve a 2:1 contrast ratio in readout is 20 erg/cm2.

The existing theory of electric conduction in solids fitted with blocking contacts has been modified to include the effect of a series resistance. Experimental current‐voltage curves for trigonal Se with indium electrodes are reported which show the essential features predicted by our theoretical analysis.

The rf magnetic susceptibility of three iron‐nickel alloys has been observed to change about one part in 104 due to space charge induced at a blocking contact.

It was observed that liquid‐crystal–photoconductor reflective light intensifiers, without optical blocking layers, become more sensitive to the imaging light when the irradiance of the actinic read‐out light is increased. Measurements illustrating the effect and an interpretation are presented.