Energy insufficiency is disturbing the improvement of Bangladesh. Since the sun light is not available always and the breeze does not blow constantly, solar and wind power alone are weaker power sources. Coupling solar as well as wind power sources along with storage batteries making up the full duration of time in the absence of wind or sun light supplies a pragmatic shape of power generation. In Bangladesh, breeze is not available most of the places. Only in the coastal areas, wind is sufficient to produce electricity. However, sunlight is available all over the year here. Although solar and wind alone power station has installed here but solar-wind cascading power station has not been installed yet.

This paper presents simulation and design for the improvement of Li-ion battery ac-tive balancer using PI controller. The growing market for lithium ion (Li-ion) battery cells has made a positive impact towards electrical energy storage (EES) system throughout the advancing technological and scientific world. Balancing in a battery pack has become a main priority to avoid over-charging and over-discharging while also improving the Li-ion battery life. Unlike passive balancing, active balancing transfers the energy from one cell to another or controls the cell’s output, thus improving its efficiency. This paper presents how previous work was accomplished by many scholars in order to avail themselves of the active balancing project. A cell model was shown in this paper that was built based on energy transfer circuit theories. A capacitor(C), inductor (L), MOSFET (M) and Diode (D) were used in the circuit build in order to balance the cells of different State-of-Charge (SOC). A PI controller was added with circuit to improve the voltage efficiency. After adding PI controller, the voltage balance of the cell was seen improved.

BACKGROUND:The association between socioeconomic status (SES), sex, race / ethnicity and outcomes during hospitalization for heart failure (HF) has not previously been investigated. METHODS AND RESULTS:We analyzed HF hospitalizations in the United States National Inpatient Sample between 2015 and 2017. Using a hierarchical, multivariable Poisson regression model to adjust for hospital- and patient-level factors, we assessed the association between SES, sex, and race / ethnicity and all-cause in-hospital mortality. We estimated the direct costs (USD) across SES groups. Among 4,287,478 HF hospitalizations, 40.8% were in high SES, 48.7% in female, and 70.0% in White patients. Relative to these comparators, low SES (homelessness or lowest quartile of median neighborhood income) (relative risk [RR] 1.02, 95% confidence interval [CI] 1.00-1.05) and male sex (RR 1.09, 95% CI 1.07-1.11) were associated with increased risk, whereas Black (RR 0.79, 95% CI 0.76-0.81) and Hispanic (RR 0.90, 95% CI 0.86-0.93) race / ethnicity were associated with a decreased risk of in-hospital mortality (5.1% of all hospitalizations). There were significant interactions between race / ethnicity and both, SES (P < .01) and sex (P = .04), such that racial/ethnic differences in outcome were more pronounced in low SES groups and in male patients. The median direct cost of admission was lower in low vs high SES groups ($9324.60 vs $10,940.40), female vs male patients ($9866.60 vs $10,217.10), and Black vs White patients ($9077.20 vs $10,019.80). The median costs increased with SES in all demographic groups primarily related to greater procedural utilization. CONCLUSIONS:SES, sex, and race / ethnicity were independently associated with in-hospital mortality during HF hospitalization, highlighting possible care disparities. Racial/ethnic differences in outcome were more pronounced in low SES groups and in male patients.

Generalized orthogonal designs have many useful applications in statistics, web engineering, and coding theory along with signal processing. In this paper, for every prime number p > 3, we develop a method of constructing a set of four circulant amicable matrices {V-i} satisfying ViViT = q(i)I(n) (I-n is the identity matrix of order n) over the prime field F(p) Using these matrices with T-matrices, we suggest some approaches to construct infinite classes of generalized orthogonal designs (GODs) over the prime fields F(p).

Advances in molecular beam epitaxy (MBE) have been crucial for the engineering of heterostructures in which the wave nature of electrons dictates carrier transport dynamics. These advances led to the first demonstration of negative differential conductance (NDC) in arsenide-based resonant tunneling diodes (RTDs) in 1974. In contrast to the 17 years elapsed between the initial MBE growth of arsenide semiconductors and the first demonstration of room-temperature GaAs/AlAs RTDs, the development of polar III-nitride RTDs has been remarkably different. After pioneering growths of nitride materials by MBE in 1973, it would take 43 years—until 2016—to demonstrate the first GaN/AlN RTD that exhibits repeatable NDC at room temperature. Here, we discuss, from the crystal growth point of view, the key developments in the epitaxy of III-nitride heterostructures that have led us to the demonstration of robust resonant tunneling transport and reliable NDC in III-nitride semiconductors. We show that in situ tracking of the crystal electron diffraction allows us to deterministically control the number of monolayers incorporated into the tunneling barriers of the active region. Employing this technique, we fabricate various GaN/AlN RTD designs showing the exponential enhancement of the resonant tunneling current as a function of barrier thickness. In addition, we experimentally demonstrate that tunneling transport in nitride RTDs is sensitive to epitaxial parameters such as the substrate growth temperature and threading dislocation density. This new insight into the MBE growth of nitride resonant tunneling devices represents a significant step forward in the engineering of new functionalities within the family of III-nitride semiconductors, allowing to harness quantum interference effects for the new generation of electronic and photonic devices.

Irradiation with deep-ultraviolet light-emitting diodes (DUV LEDs) is emerging as a low energy, chemical-free approach to mitigate microbial contamination, but the effect of surface conditions on treatment effectiveness is not well understood. Here, inactivation of L. innocua and E. coli ATCC25922, as examples of Gram-positive and Gram-negative bacteria, respectively, by DUV LED of 280 nm wavelength was studied. Surface scenarios commonly encountered in environmental, clinical or food processing environments were used: nutrient rich surfaces, thin liquid films (TLF), and stainless steel surfaces (SS). DUV LED exposure achieved 5-log reduction for both strains within 10 min in most scenarios, except for TLF thicker than 0.6 mm. Inactivation kinetics in TLF and on dry SS followed the Weibull model (0.96 ≤ R 2 ≤ 0.99), but the model overestimated inactivation by small-dose DUV on wet SS. Confocal microscopy revealed in situ that bacteria formed a dense outer layer at the liquid-air interface of the liquid droplet, protecting the cells inside the droplet from the bactericidal DUV. This resulted in lower than anticipated inactivation on wet SS at small DUV doses, and deviation from the Weibull model. These findings can be used to design effective DUV LED disinfection strategies for various surface conditions and applications.

We report optically and electrically pumped ∼ 280 n m deep ultraviolet (DUV) light emitting diodes (LEDs) with ultra-thin GaN/AlN quantum disks (QDs) inserted into AlGaN nanorods by selective epitaxial regrowth using molecular beam epitaxy. The GaN/AlN QD LED has shown strong DUV emission distribution on the ordered nanorods and high internal quantum efficiency of 81.2%, as a result of strain release and reduced density of threading dislocations revealed by transmission electron microscopy. Nanorod assembly suppresses the lateral guiding mode of light, and light extraction efficiency can be increased from 14.9% for planar DUV LEDs to 49.6% for nanorod DUV LEDs estimated by finite difference time domain simulations. Presented results offer the potential to solve the issue of external quantum efficiency limitation of DUV LED devices.

We demonstrate coupling to and control over the broadening and dispersion of a mid-infrared leaky mode, known as the Berreman mode, in samples with different dielectric environments. We fabricate subwavelength films of AlN, a mid-infrared epsilon-near-zero material that supports the Berreman mode, on materials with a weakly negative permittivity, strongly negative permittivity, and positive permittivity. Additionally, we incorporate ultra-thin AlN layers into a GaN/AlN heterostructure, engineering the dielectric environment above and below the AlN. In each of the samples, coupling to the Berreman mode is observed in angle-dependent reflection measurements at wavelengths near the longitudinal optical phonon energy. The measured dispersion of the Berreman mode agrees well with numerical modes. Differences in the dispersion and broadening for the different materials is quantified, including a 13 cm-1 red-shift in the energy of the Berreman mode for the heterostructure sample.

Deep ultraviolet light-emitting diodes (200–280 nm) have many potential applications in diagnostics, therapeutics, security, and tanning. But, the state-of-the-art LEDs suffer from low external quantum efficiency (< 20%). The external quantum efficiency is composed of internal quantum efficiency, injection efficiency, and the light extraction efficiency. These components are limited due to fundamental material and physics-based challenges. In this chapter, a set of novel heterostructure designs are presented to improve the individual efficiency components that compose the external quantum efficiency. Theoretical analysis followed by crystal growth and experimental data are presented showing enhancement of each efficiency components. Inclusion of such new design techniques will enhance the external quantum efficiency of deep-UV light emitters.

Deep ultraviolet light-emitting diodes (LEDs) composed of III-Nitride semiconductors need layers of heavy doping (>1 × 1019 cm−3) to overcome large dopant activation energies and maintain high electrical conductivity. This work reports that at doping densities of [Si] ∼1.5 × 1019/cm3 for n-Al0.7Ga0.3N, Burstein-Moss and bandgap renormalization effects result in a net reduction of the bandgap of ∼70 meV. At these doping levels, a transition to a metallic conductivity state is observed, with a vanishing of the effective dopant activation energy. The sheet and contact resistivities of Rsh,n = 0.045 Ω cm and ρc,n = 1.13 × 10−6 Ω cm2 are achieved, with uniform conductivity in the vertical direction. The results show that when heavily doped n-AlGaN cladding regions are used for high efficiency deep-UV LEDs or lasers, the accompanying bandgap narrowing reduces the window of optical transparency at the lowest wavelengths that can take advantage of high conductivity.

Aluminum nitride (AlN) plays a key role in modern power electronics and deep-ultraviolet photonics, where an understanding of its thermal properties is essential. Here, we measure the thermal conductivity of crystalline AlN by the 3ω method, finding that it ranges from 674 ± 56 Wm−1 K−1 at 100 K to 186 ± 7 Wm−1 K−1 at 400 K, with a value of 237 ± 6 Wm−1 K−1 at room temperature. We compare these data with analytical models and first-principles calculations, taking into account atomic-scale defects (O, Si, C impurities, and Al vacancies). We find that Al vacancies play the greatest role in reducing thermal conductivity because of the largest mass-difference scattering. Modeling also reveals that 10% of heat conduction is contributed by phonons with long mean free paths (MFPs), over ∼7 μm at room temperature, and 50% by phonons with MFPs over ∼0.3 μm. Consequently, the effective thermal conductivity of AlN is strongly reduced in submicrometer thin films or devices due to phonon-boundary scattering.

Polymer dielectrics find applications in modern electronic and electrical technologies due to their low density, durability, high dielectric breakdown strength, and design flexibility. However, they are not reliable at high temperatures due to their low mechanical integrity and thermal stability. Herein, a self‐assembled dielectric nanocomposite is reported, which integrates 1D polyaramid nanofibers and 2D boron nitride nanosheets through a vacuum‐assisted layer‐by‐layer infiltration process. The resulting nanocomposite exhibits hierarchical stacking between the 2D nanosheets and 1D nanofibers. Specifically, the 2D nanosheets provide a thermally conductive network while the 1D nanofibers provide mechanical flexibility and robustness through entangled nanofiber–nanosheet morphologies. Experiments and density functional theory show that the nanocomposites through thickness heat transfer processes are nearly identical to that of boron nitride due to synergistic stacking of polyaramid units onto boron nitride nanosheets through van der Waals interactions. The nanocomposite sheets outperform conventional dielectric polymers in terms of mechanical properties (about 4–20‐fold increase of stiffness), light weight (density ≈1.01 g cm−3), dielectric stability over a broad range of temperature (25–200 °C) and frequencies (103–106 Hz), good dielectric breakdown strength (≈292 MV m−1), and excellent thermal management capability (about 5–24 times higher thermal conductivity) such as fast heat dissipation.

Thermal activation of buried p-type GaN is investigated in metal-organic chemical vapor deposition-regrown vertical structures, where the buried p-GaN is re-passivated by hydrogen during regrowth. The activation is performed by exposing the buried p-GaN through etched sidewalls and characterized by reverse breakdown measurements on vertical diodes. The effect of the n-type doping level on the activation has been observed. After 725 °C/30 min annealing in a dry air environment, the buried p-GaN with a regrown unintentionally-doped (UID) capping layer is sufficiently activated due to significant Mg-incorporation in the UID layer, allowing for hydrogen up-diffusion. With an additional regrown n+-GaN capping layer (i.e., in n+/i/p-n diodes), only lateral diffusion of H out of the exposed mesa sidewall is permitted. A critical lateral dimension between 10 and 20 μm is found for the n+/i/p-n diodes, under which the buried p-GaN is sufficiently activated. The diodes with activated buried p-GaN achieved up to 1200 V breakdown voltage, indicating that over 28% of the Mg dopants is activated. The study demonstrates the effectiveness of sidewall p-GaN activation in achieving high breakdown voltage pertinent to GaN vertical power devices, while providing guidelines on the required device geometry.

Deep ultraviolet (DUV) AlN-delta-GaN quantum well (QW) light-emitting diodes (LEDs) with emission wavelengths of 234 nm and 246 nm are proposed and demonstrated in this work. Our results reveal that the use of AlN-delta-GaN QW with ∼1–3 monolayer GaN delta-layer can achieve a large transverse electric (TE)-polarized spontaneous emission rate instead of transverse magnetic-polarized emission, contrary to what is observed in conventional AlGaN QW in the 230–250 nm wavelength regime. The switching of light polarization in the proposed AlN-delta-GaN QW active region is attributed to the rearrangement of the valence subbands near the Γ-point. The light radiation patterns obtained from angle-dependent electroluminescence measurements for the Molecular Beam Epitaxy (MBE)-grown 234 nm and 246 nm AlN-delta-GaN QW LEDs show that the photons are mainly emitted towards the surface rather than the edge, consistent with the simulated patterns achieved by the finite-difference time-domain modeling. The results demonstrate that the proposed AlN-delta-GaN QWs would potentially lead to high-efficiency TE-polarized surface-emitting DUV LEDs.

III-nitride ultraviolet (UV) light emitting diodes (LEDs) with emission wavelengths in the range of 250-280 nm have attracted considerable interest for applications such as germicidal disinfection and biological detection. However, the widely-used AlGaN quantum well (QW)-based LEDs at such wavelengths suffer from low quantum efficiencies. One main factor that limits the AlGaN QW LED efficiency at ~250-280 nm is the suffering of the severe band mixing effect caused by the valence subbands crossover, as well as the Quantum Confined Stark Effect (QCSE). Therefore, the novel AlGaN-delta-GaN QW design was proposed to address these issues in order to realize high-efficiency deep-UV LEDs. Here, we proposed a novel Al0.9Ga0.1N-delta-GaN QW by inserting an ultra-thin delta-GaN layer into a conventional Al0.9Ga0.1N QW active region. The physics from such QW design was investigated by 6-band k·p model and the structure was experimentally demonstrated by Plasma-assisted Molecular Beam Epitaxy (PAMBE). The calculated results show that the insertion of delta-GaN layer could successfully address the band mixing issue and QCSE, leading to a significant improvement in spontaneous emission rate as compared to that of Al0.55Ga0.45N QW at 260 nm. The 5-period Al0.9Ga0.1N-delta-GaN QW with 3-nm AlN barrier was grown on AlN/sapphire substrate by MBE with ~2-monolayer delta-GaN layer, which was evidenced by the cross-sectional transmission electron microscope. The two-photon photoluminescence spectrum presented a single peak emission centered at 260 nm from the grown Al0.9Ga0.1N-deltaGaN QW with a full width at half maximum of 12 nm, which shows that the demonstrated QW would be promising for high-efficiency UV LEDs.

We report the generation of room temperature microwave oscillations from GaN/AlN resonant tunneling diodes, which exhibit record-high peak current densities. The tunneling heterostructure grown by molecular beam epitaxy on freestanding GaN substrates comprises a thin GaN quantum well embedded between two AlN tunneling barriers. The room temperature current-voltage characteristics exhibit a record-high maximum peak current density of ∼220 kA/cm2. When biased within the negative differential conductance region, microwave oscillations are measured with a fundamental frequency of ∼0.94 GHz, generating an output power of ∼3.0 μW. Both the fundamental frequency and the output power of the oscillator are limited by the external biasing circuit. Using a small-signal equivalent circuit model, the maximum intrinsic frequency of oscillation for these diodes is predicted to be ∼200 GHz. This work represents a significant step towards microwave power generation enabled by resonant tunneling transport, an ultra-fast process that goes beyond the limitations of current III-Nitride high electron mobility transistors.

GaN vertical trench-MOSFETs incorporating molecular beam epitaxy (MBE) regrown channel are developed and investigated. The channel regrowth by MBE prevents repassivation of the p-type GaN body while promising higher channel mobility. Two different designs of the lateral portion of the regrown channel are compared: without or with an n+-GaN buried layer. Without an n+ buried layer, a respectable 600-V breakdown voltage (BV) is measured in the absence of edge termination, indicating a decent critical field strength (>1.6 MV/cm) of the regrown channel. However, the ON-resistance is limited by the highly resistive lateral channel due to Mg incorporation. With an n+ buried layer, the limitation is removed. Excellent ON-current of 130 mA/mm and ON-resistivity of $6.4 ~\rm {m\Omega \cdot cm^{2}}$ are demonstrated. The BV is limited by high source–drain leakage current from the channel due to drain-induced barrier lowering (DIBL) effect. Device analysis together with TCAD simulations points out the major cause for the DIBL effect: the presence of interface charge beyond a critical value ( $\sim 6\times 10^{12}\,\,\rm {cm^{-2}}$ ) at the regrowth interface on etched sidewalls. This paper provides valuable insights into the design of GaN vertical trench-MOSFET with a regrown channel, where simultaneous achievement of low ON-resistivity and high BV is expected in devices with reduced interface charge density and improved channel design to eliminate DIBL.

III-nitride based ultraviolet (UV) light emitting diodes (LEDs) are of considerable interest in replacing gas lasers and mercury lamps for numerous applications. Specifically, AlGaN quantum well (QW) based LEDs have been developed extensively but the external quantum efficiencies of which remain less than 10% for wavelengths <300 nm due to high dislocation density, difficult p-type doping and most importantly, the physics and band structure from the three degeneration valence subbands. One solution to address this issue at deep UV wavelengths is by the use of the AlGaN-delta-GaN QW where the insertion of the delta-GaN layer can ensure the dominant conduction band (C) - heavyhole (HH) transition, leading to large transverse-electric (TE) optical output. Here, we proposed and investigated the physics and polarization-dependent optical characterizations of AlN-delta- GaN QW UV LED at ~300 nm. The LED structure is grown by Molecular Beam Epitaxy (MBE) where the delta-GaN layer is ~3-4 monolayer (QW-like) sandwiched by 2.5-nm AlN sub-QW layers. The physics analysis shows that the use of AlN-delta-GaN QW ensures a larger separation between the top HH subband and lower-energy bands, and strongly localizes the electron and HH wave functions toward the QW center and hence resulting in ~30-time enhancement in TEpolarized spontaneous emission rate, compared to that of a conventional Al0.35Ga0.65N QW. The polarization-dependent electroluminescence measurements confirm our theoretical analysis; a dominant TE-polarized emission was obtained at 298 nm with a minimum transverse-magnetic (TM) polarized emission, indicating the feasibility of high-efficiency TEpolarized UV emitters based on our proposed QW structure.

Future generations of ultra-scaled logic may require alternative device technologies to transcend the limitations of Si CMOS; in particular, power dissipation constraints in aggressively-scaled, highly-integrated systems make device concepts capable of achieving switching slopes (SS) steeper than 60 mV/decade especially attractive. Tunneling field effect transistors (TFETs) are one such device technology alternative. While a great deal of research into TFETs based on Si, Ge, and narrow band gap III-Vs has been reported, these approaches each face significant challenges. An alternative approach based on the use of III-N wide band gap semiconductors in conjunction with polarization engineering offers potential advantages in terms of drain current density and switching slope. In this talk, the prospects for III-N based TFETs for logic will be discussed, including both simulation projections as well as experimental progress.

We demonstrate a 243 nm deep-ultraviolet (deep-UV) GaN/AlN heterostructure light-emitting diode with and without a tunnel-junction p-contact. Optical emission occurs from 2 monolayer thick GaN quantum structure active regions. Use of a tunnel-junction enhances the current density under forward bias.