The hexagonal boron nitride (h-BN) as a wide bandgap semiconductor is an attractive material for deep ultraviolet (DUV) generation. In this paper we study the prospect of using the stacking hexagonal boron nitride nanosheets (h-BNNS) for generating DUV emission by impact excitation in alternating current driven thin electroluminescence devices (ACTEL) based on BN phosphors having different morphologies. A theoretical approach considered is based on the impact excitation model for generating DUV from stacking h-BNNS under a high electric field. It was found that in the h-BNNS with a thickness of 90 nm biased at 3.33×109 V/m, the quantum yield can reach to 86.8%, and the power conversion efficiency of 1.68%. To achieve the same quantum yield and power conversion efficiency for the ACTEL based on h-BN single crystal, the active phosphor layer should be 2 μm thick when biased at 1.5×108 V/m.

Cubic gallium nitride (GaN) is a wide bandgap semiconductor that exhibits a high crystallographic symmetry resulting in a lower inbuilt polarization which is useful for more efficient phosphor-free green light-emitting diodes. It has been grown using molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD), which produce highly ordered thin films on compatible substrates. In this work, we report the chemical synthesis of GaN using chemical metathesis reaction in diethyl ether with lithium nitride and anhydrous gallium chloride as precursors, inside a nitrogen glove box at the room temperature. The resulting product was subsequently washed to remove lithium chloride and dried before vacuum annealing in a furnace at 850°C. Powder X-ray diffraction (XRD) scans of the as-prepared and annealed product reveal a mixed phase of GaN along with Ga2O3. Energy dispersive X-ray spectroscopy (EDAX) measurements show a nitrogen-poor product, which correlates well with the nearly black color of the powder. Diffuse reflectance spectroscopy (DRS) measurements were carried out with the obtained product on a barium sulfate substrate in a Perkin-Elmer Lambda 1050-UV-Vis-NIR spectrophotometer showing a strong absorbance below 400 nm. The energy band gap is bounded by values extracted from the Tauc plot and DRS measurements in the range of 3.2-3.5 eV, which is in good agreement with the known excitonic bandgap of cubic GaN (∼ 3.3 eV). Initial photoluminescence (PL) measurements using a Perkin-Elmer LS-55 spectrophotometer with an excitation wavelength of 310 nm reveal a weak emission centered around 440 nm corresponding to the known defect centers (D0X) in GaN. Further development of this process to form inks is expected to provide an alternate pathway to producing flexible phosphor-free lighting devices.

Resistance switching random-access memory (ReRAM), with the ability to repeatedly modulate electrical resistance, has been highlighted as a feasible high-density memory with the potential to replace negative-AND flash memory. Such resistance modulation usually involves ion migration and filament formation, which usually lead to relatively low device reliability and yield. Resistance switching can also come from an entirely electronic origin, as in nanometallic memory, by electron trapping and detrapping. Recent research has revealed additional merits of its mechanism, which entails smart, atomic-sized floating gates that can be easily engineered in amorphous Si, oxides, and nitrides. This article addresses the basic ideas of nanometallic ReRAM, which may also be a contender for analogue computing and non-von Neumann-type computation.

The transconductance degradation caused by the non-linear resistance of access regions in III-nitride high electron-mobility transistors (HEMTs) is mainly responsible for limiting the RF linearity of the transistor. In this paper, we use Landauer’s transmission theory to develop an analytic electrothermal current-voltage (I-V) model of access regions in III-nitride HEMTs. With only 12 parameters, most of which have a physical origin and can be obtained through experimental calibration, the model is able to correctly predict the I-V behavior in access regions from the drift-diffusive to the quasi-ballistic transport regimes. Model accuracy is demonstrated by comparing the results against experimental and numerical hydrodynamic simulations of ungated transmission line structures with length scales ranging from few 10’s of nanometers to 10’s of micrometers.

This research shows the development of alternative Cu-based materials for applications where enhanced thermal properties are desired. Cu/AlN composites were fabricated from mixtures of pure Cu and copper plated AlN-Cu composite powders. The ceramic phase was added in amounts of 10, 20 and 30 vol.% and the mixtures sintered by pulsed electric current sintering process (PECS). The results showed that the AlN particles are homogeneously distributed in the copper matrix and that the true contacts between hard particles are reduced because of the deposited copper on their surfaces, improving the connectivity of the matrix phase and bonding at the metal-ceramic interface. The relative density of the Cu/AlN composites was major than 97% in all cases. Thermal conductivity of the composites was high and decreased with the ceramic content from 359 to 194 W/mK, for 10 and 30% AlN, respectively. The coefficient of thermal expansion followed a lineal behavior with temperature and is also reduced with the ceramic content.

Recently, Plasma Assisted Atomic Layer Deposition Technique will easily control the thickness and the composition of semiconductor films. The radical generated by using the plasma techniques, gave the decrease of the defect into the semiconductor films. In this investigation, the relationship between microwave plasma power, nitrogen gas flow rate and concentration of generated nitrogen radical, was evaluated. At the first, Plasma emission spectrum at microwave plasma power (0 to 400W) was measured using a mixed 200sccm argon gas and 10sccm nitrogen gas. Next, the plasma emission spectrum was measured in the mixing of nitrogen gas flow rate (0 to 40sccm) with 200sccm argon gas flow rate. At that time, the microwave plasma power was set to 200W. Nitrogen radical spectrum were identified from all the emission spectrum, and the nitrogen radical intensity was calculated. As a result, the nitrogen radical intensity became the largest at 200sccm argon gas flow rate and 10sccm nitrogen gas flow rate. In addition, the nitrogen radical intensity increased in proportion to the microwave plasma power. The concentration of generated nitrogen radical could be controlled by changing the microwave plasma power and the nitrogen gas flow rate. Mentioned above, nitride thin films will be obtained on Si Substrates by microwave generated remote plasma assisted atomic layer deposition technique.

Anomalous Hall effect was observed at room temperature in MOCVD-grown GaGdN from a (TMHD)3Gd source, which can contain oxygen in its organic ligand. GaN, and GaGdN grown using a Cp3Gd precursor which does not contain oxygen only showed the ordinary Hall effect. This indicates that oxygen could have a role in magnetic properties of GaGdN. The relationship between the anomalous Hall conductivity and longitudinal conductivity indicated that metallic conduction, hopping of carriers, and scattering-independent mechanisms are likely responsible for the ferromagnetism. However, this still requires further clarification.

We analyze the microscopic origins of subgap photoexcitations of individual gallium nitride (GaN) triangular cross-section nanowires (NWs), which are highly photoactive over a broadband spectral range. Using confocal hyperspectral photoluminescence (PL) microscopy, mid-gap states on the NWs were excited using subgap illumination, resulting in two distinct PL spectra corresponding to the polar (0001) and the semipolar $\left( {\bar 1101} \right)$ / $\left( {1\bar 101} \right)$ surfaces. Emission spectra are well represented by Gaussian functions with fitted centers of 1.99 ± 0.01 eV and 2.26 ± 0.01 eV, respectively. PL collected from the end facets exhibits interference fringes and a relative blue shift. Furthermore, the PL spectrum shifts strongly to the blue when the excitation intensity is increased. These observations are consistent with a qualitative model in which the PL results from excitation into a broad manifold of surface-associated states which are rapidly populated at a high excitation intensity and can couple to etalon modes via longitudinal photon emission.

Pulsed laser deposition is one of the most flexible growth methods for high-quality epitaxial multifunctional thin films and short-period superlattices. The following examples of current research interest demonstrate the state-of-the art: First, it is shown that the magnetoelectric performance of multiferroic BiFeO3–BaTiO3 (001)-oriented superlattices depends on the crystalline coherence of the different layers at the interfaces. Second, it is exemplified that dielectric-plasmonic superlattices built from the electrically insulating oxide MgO and the metallically conducting nitride TiN are promising metamaterials with hyperbolic dispersion. As a third example, it is demonstrated that LaNiO3- and LaMnO3-based superlattices with (001)-, (011)-, and (111)-out-of-plane orientation and controlled single layer thickness from 2 to 15 atomic monolayers show metal-insulator transitions and tunable gaps, in partial agreement with density functional theory calculations. Underlined by these examples, it is shown that the precise control of an epitaxially coherent, or two-dimensional layer-by-layer growth, named after Jan van der Merwe, is a prerequisite to achieve the desired functionality of oxide–oxide and oxide–nitride superlattices.

It is important to fabricate iron-based nitride/conductive material composite to obtain good catalytic performance. In this work, Fe2N nanoparticles with diameter of approximately 30 nm have been successfully dispersed on the surface of nitrogen-doped graphite oxide (NrGO) by a facile sol–gel method and further ammonia atmosphere treatment. XPS, XRD, Raman, and TEM proved that Fe2N nanoparticles are well monodispersed, and nitrogen atoms are doped in NrGO. The composite possessed two merits, that is, the more catalytic active site in Fe2N nanoparticles due to the well monodispersion, and fast electron transfer due to the nitrogen dope in rGO. With the proper ratio, the composite exhibited brilliant catalytic activity and durability in acidic media. It possesses overpotential of 94 mV to approach 10 mA/cm2, a small Tefel slope of 49 mV/dec, and maintains the good electrocatalytic activity for 10 h. Cyclic voltammetry and electrochemical impedance spectroscopy indicated that the electrocatalyst possessed high catalytic active area and fast electron transfer. Our work may provide a new avenue for the preparation of low-cost iron-based nitride/NrGO composite for highly efficient electrochemical hydrogen evolution.

The surface hardening of Cu is an effective way to keep good electrical conductivity and increase chemical inertness. Here, Cr and Zr are introduced into Cu films to stabilize N and increase the film hardness. CuN-based alloy films are prepared on single-crystal Si(100) substrates using magnetron sputtering. Cu(Cr, N) films are mainly composed of Cu and Cr2N nanocrystals while Cu and Zr2N nanocrystals compose Cu(Zr, N) films. The thermal stability of the ternary films comes from the strong interaction between Cr (or Zr) and N which is contributing to the generation of stable nitrides. In terms of resistivity and hardness, the Cu(Cr, N) and Cu(Zr, N) films prepared at the N2/Ar ratio of 1/10 show preferable properties. Especially, the Cu86.1Zr6.1N7.8 film exhibits the highest hardness (∼4.7 GPa) and lowest resistivity (63.6 μΩ·cm). The chemical inertness of Cu film can also be improved by adding Cr–N and Zr–N. These ternary films are expected to apply for Cu surface nitrogenization.

In0.06Ga0.94N/GaN superlattices (SLs) grown on sapphire (0001) by metalorganic chemical vapor deposition were studied before and after europium (Eu) ion implantation to understand the strain induced-effects in the SL structure. The implanted SLs were investigated as a function of the thermal annealing temperature up to 1000 °C in nitrogen ambient. Temperature dependent photoluminescence spectra showed a red-shift of the SL emission peaks due the quantum confined Stark effect, followed by a blue-shift due to In atoms out-diffusion from the In0.06Ga0.94N quantum well, for both Eu ions implanted and unimplanted SLs. The amplitude of observed spectral shifts was smaller and the line width of the SLs emission peaks were narrower in the SLs:Eu3+ as compared to the unimplanted SLs. It is concluded that Eu3+ ions modified the strain in the SLs acting like impurity and/or defects getter in implantation degraded SLs resulting in material phase purification and improvements of SLs optical properties.

Silicon Nitride based charge trap devices have been studied since the 1980s for applications in non-volatile memories. Silicon-Oxide-Nitride-Oxide-Silicon (SONOS) stack as the non-volatile memory gate stack has been the focus since the 1990s. Several enhancements in SONOS layer materials have been invented to reduce the programming voltage and improve the reliability of the SONOS memory. SONOS memories are a widely used class of non-volatile memories today. This paper will review the history of SONOS and highlight the various innovations that have enhanced SONOS memory performance, reliability and low cost of manufacture. Topics covered include various improvements in the SONOS stack such as Band gap engineering, High K–Metal Gate for SONOS, 3D SONOS, SONOS FinFETs (Field Effect Transistor) and embedded SONOS.

AlGaN based multiple quantum wells (MQWs) were grown on 8° vicinal 4H p-SiC substrates by plasma-assisted molecular beam epitaxy. The MQWs were designed to emit near 300 nm using the wurtzite k.p model. The MQW periodicity and strain state were measured with X-ray diffraction. The optical properties were characterized with temperature dependent photoluminescence (PL). The internal quantum efficiency was estimated from the ratio of room temperature to 18K integrated PL intensity. Internal quantum efficiency up to 48% was achieved. These data are encouraging for future vertical and inverted ultraviolet light emitting diodes grown on p-SiC substrates.

Phase separation of InxGa1−xN into Ga-rich and In-rich regions has been studied by electron energy-loss spectroscopy (EELS) in a monochromated, aberration corrected scanning transmission electron microscope (STEM). We analyze the full spectral information contained in EELS of InGaN, combining for the first time studies of high-energy and low-energy ionization edges, plasmon, and valence losses. Elemental maps of the N K, In M4,5 and Ga L2,3 edges recorded by spectrum imaging at 100 kV reveal sub-nm fluctuations of the local indium content. The low energetic edges of Ga M4,5 and In N4,5 partially overlap with the plasmon peaks. Both have been fitted iteratively to a linear superimposition of reference spectra for GaN, InN, and InGaN, providing a direct measurement of phase separation at the nm-scale. Bandgap measurements are limited in real space by scattering delocalization rather than the electron beam size to ∼10 nm for small bandgaps, and their energetic accuracy by the method of fitting the onset of the joint density of states rather than energy resolution. For an In0.62Ga0.38N thin film we show that phase separation occurs on several length scales.

Our study proposes in situ synthesis of cold-rollable aluminum nitride (AlN) reinforced aluminum matrix composites with attractive thermal properties via arc plasma-induced accelerated volume nitridation (APAVN). Within three minutes of repeated APAVN using commercial nitrogen gas, volume fraction of AlN increased up to 40 vol%, which is the highest value ever reported by in situ nitridation of pure aluminum. The composites contained homogeneously dispersed AlN particulates with strong interfacial bonding and low interfacial thermal resistance, which resulted in unique combination of a relatively low coefficient of thermal expansion and high specific thermal conductivity. APAVN resulted from instantaneous chemisorption of dissociated nitrogen, enhanced diffusion of dissolved nitrogen, and improved wettability, which led to much more AlN formation, ∼2.94 × 10−1 g/(min cm3), which is about 400 times higher than that in the gas bubbling method. These results would ultimately give us a promising strategy for continuous production of in situ Al–AlN composites for heat sink applications through cost-effective processing.

AlGaN/GaN heterostructures were grown by metal–organic chemical vapor deposition (MOCVD) on sp2-bonded BN using AlN as a nucleation layer. The best x-ray diffraction rocking curve full-width-at-half-maximums (FWHMs) are 0.13° and 0.17° for the GaN (0002) and ( $10\bar 12$ ) diffraction peaks. Hall-effect measurements show room temperature mobility near 2000 cm/V·s with sheet carrier density of ∼1 × 1013 cm−2, comparable to the best values obtained on sapphire using Fe-doped GaN buffers. The best low temperature mobility of the 2-dimensional electron gas (2DEG) is ∼33,000 cm2/V·s; indicating that the dominant scattering mechanism limiting the transport of 2DEG is interface roughness. Good quality BN grown directly onto sapphire is shown to be effective for reducing parallel conduction that exists due to residual donor impurities in the buffer. Luminescence measurements indicate good optical quality of the GaN/BN/sapphire. The residual strain in the GaN layer is found to be almost completely eliminated when it is released from the substrate.

The mesoporous network within photocatalytically and photoelectrochemically active LaTiO2N (LTON) single crystals was investigated by electron microscopy techniques including electron diffraction and scanning transmission electron microscopy imaging. The perovskite-related oxynitride particles were obtained by thermal ammonolysis from monocrystalline micrometer-sized La2Ti2O7 (LTO) particles grown by flux-assisted solid state synthesis. Special attention was paid to the crystal transformation from the monoclinic layered LTO to the orthorhombic perovskite-related LTON within the monocrystalline particles. A detailed analysis of pore directions and pore sizes with respect to the LTON particle shape was performed. The pore formation mechanism taking place during thermal ammonolysis was discussed. Based on the mechanistic understanding of the transformation from the oxide to the oxynitride, a further extension of the mesoporous network toward higher surface areas was proposed for improved photoelectrochemical activity of oxynitride particles, while high crystallinity and particle sizes in the micrometer range continue to enable efficient charge transport.

In recent years titanium nitride is being considered as a very promisingplasmonic material for data storage applications as it exhibits a pronouncedplasmonic dipolar resonance and has high thermal stability. However, there is alack of research where higher order resonance modes are examined. We addressthis here by performing angle dependent spectral transmission measurementsnanodisks arrays made from titanium nitride. The measurements show strongpolarization dependence with s-polarized light causing excitation of thequadrupole and higher order resonance plasmonic modes. These higher order modesare required for the state-of-the-art designs of near-field transducers. This,together with its outstanding thermal properties, makes TiN a favourablematerial for data storage applications.

GaN has emerged as the material of choice for advanced power amplifier devicesfor both industrial and defense applications but near-junction thermal barriersseverely limit the inherent capability of high-quality GaN materials. Recent“embedded cooling” efforts, funded by Defense AdvancedResearch Projects Agency Microsystems Technology Office (DARPA-MTO), havefocused on reduction of this near-junction thermal resistance, through the useof diamond substrates and efficient removal of the dissipated power withconvective and evaporative microfluidics. An overview of the accomplishments ofthe DARPA Near-Junction Thermal Transport (NJTT) program and recent results fromthe on-going DARPA Intra-Chip Embedded Cooling (ICECool) program are provided.It is shown that growth or bonding of diamond to GaN epitaxy has enabled a3-5× increase in power handling capability per transistor unit area,while use of microfluidic cooling has enabled heat fluxes of 30kW/cm2 at the transistor level and 1 kW/cm2 at thedie-level, for a 3-6× improvement in the total RF output power of GaNpower amplifiers. These demonstrations provide near-term validation of the largeimprovement in output power gained through embedded cooling and confirm thepotential for well above a 6× improvement in GaN power amplifier outputpower to the electrical, rather than thermal, limits of GaN.