Normally-off p-GaN Gated AlGaN/GaN MIS-HEMTs with ALD-Grown Al2O3/AlN Composite Gate Insulator

A metal–insulator–semiconductor p-type GaN gate high-electron-mobility transistor (MIS-HEMT) with an Al2O3/AlN gate insulator layer deposited through atomic layer deposition was investigated. A favorable interface was observed between the selected insulator, atomic layer deposition–grown AlN, and GaN. A conventional p-type enhancement-mode GaN device without an Al2O3/AlN layer, known as a Schottky gate (SG) p-GaN HEMT, was also fabricated for comparison. Because of the presence of the Al2O3/AlN layer, the gate leakage and threshold voltage of the MIS-HEMT improved more than those of the SG-HEMT did. Additionally, a high turn-on voltage was obtained. The MIS-HEMT was shown to be reliable with a long lifetime. Hence, growing a high-quality Al2O3/AlN layer in an HEMT can help realize a high-performance enhancement-mode transistor with high stability, a large gate swing region, and high reliability.

Radio-Oxidation Ageing of XLPE Containing Different Additives and Filler: Effect on the Gases Emission and Consumption

In the lifetime extension of nuclear power plants (NPPs) context, aging of electric cables has to be very well understood in order to predict their end-of-life and thus to replace them on time. Therefore, evaluation and understanding of the ageing mechanism of the cable insulating material is mandatory under conditions as close as possible of those encountered in NPPs. In this context, different formulated crosslinked polyethylenes (XLPE)—one of the polymers used nowadays to manufacture the insulator layer—have been irradiated under oxidative conditions, at two different dose rates and at different aging doses. Gases emitted and consumed from the irradiated polymers were quantified to identify the primary processes happening in the materials and thus the interactions involved between the different molecules composing the formulated polymers.

Frequency and Voltage-dependent Electrical Parameters, Interface Traps, and Series Resistance Profile of Au/(NiS:PVP)/n-Si Structures

A thin (NiS-doped PVP) interface layer was spin-coated on n-Si substrate and between Au contact were prepared on the surface by the sputtering method and then their basic electrical features for example diffusion-potential (VD), doping density of donor-atoms (ND), Fermi-energy (EF), barrier-height (ΦB), and depletion layer-width (WD) were extracted reverse-bias C-2-V plots as function frequency and voltage. The voltage profile of interface/surface-states (Nss)/ relaxation-times (τ), and series resistance (Rs) were also obtained from the admittance and Nicollian-Brews method, respectively. Strongly frequency-dependent and voltage especially in both accumulation and depletion regions due to the existence of Nss, Rs, and polarization as well as (NiS-doped PVP) organic interlayer. At low frequency, the observed higher value of C and G shows that thin (NiS:PVP) interlayer can be successfully used to obtain high charges/energy storage (MPS) structure/capacitor instead of conventional insulator layer performed traditional methods. As a result, the observed important changes in electrical parameters with frequency and voltage depend on Nss, their t, Rs, organic interlayer, and interfacial or dipole polarization.

Cobalt Metal ALD: Understanding the Mechanism and Role of Zink Alkyl Precursors as Reductants for Low Resistivity Co Thin Films

In this work, we report a new and promising approach towards the atomic layer deposition (ALD) of metallic Co thin films. Utilizing the simple and known CoCl₂(TMEDA) (TMEDA = N,N,N’,N’-tetramethylethylenediamine) precursor in combination with the intramolecularly stabilized Zn aminoalkyl compound Zn(DMP)₂ (DMP = dimethylaminopropyl) as auxiliary reducing agent, a thermal ALD process is developed that enables the deposition of Zn free Co thin films. ALD studies demonstrate the saturation behavior of both precursors, linearity in dependency of the applied number of cycles as well as investigations of the temperature dependency of film growth in a regime of 140 - 215 °C. While the process optimization is carried out on Si with native oxide, additional growth studies are conducted on Au and Pt substrates. This study is complemented by initial reactivity and suitability tests of several potential Zn alkyl reducing agents. For the CoCl₂(TMEDA) - Zn(DMP)₂ combination, these findings allow to propose a series of elemental reaction steps hypothetically leading to pure Co film formation in the ALD process whose feasibility are probed by a set of DFT calculations. The DFT results show that for reactions of the precursors in the gas phase and on Co(111) substrate surfaces, a pathway involving C-C coupling and diamine formation through reductive elimination of an intermediate Co(II) alkyl species is preferred. Co thin films with an average thickness of 10 - 25 nm obtained from the process are subjected to thorough analysis comprising AFM, SEM, RBS/NRA as well as depth profiling XPS. Resistivity measurements for ~ 22 nm thick films grown on a defined SiO₂ insulator layer yield highly promising values in a range of 15 - 20 μΩ cm without any after treatment.

Cobalt Metal ALD: Understanding the Mechanism and Role of Zink Alkyl Precursors as Reductants for Low Resistivity Co Thin Films

In this work, we report a new and promising approach towards the atomic layer deposition (ALD) of metallic Co thin films. Utilizing the simple and known CoCl₂(TMEDA) (TMEDA = N,N,N’,N’-tetramethylethylenediamine) precursor in combination with the intramolecularly stabilized Zn aminoalkyl compound Zn(DMP)₂ (DMP = dimethylaminopropyl) as auxiliary reducing agent, a thermal ALD process is developed that enables the deposition of Zn free Co thin films. ALD studies demonstrate the saturation behavior of both precursors, linearity in dependency of the applied number of cycles as well as investigations of the temperature dependency of film growth in a regime of 140 - 215 °C. While the process optimization is carried out on Si with native oxide, additional growth studies are conducted on Au and Pt substrates. This study is complemented by initial reactivity and suitability tests of several potential Zn alkyl reducing agents. For the CoCl₂(TMEDA) - Zn(DMP)₂ combination, these findings allow to propose a series of elemental reaction steps hypothetically leading to pure Co film formation in the ALD process whose feasibility are probed by a set of DFT calculations. The DFT results show that for reactions of the precursors in the gas phase and on Co(111) substrate surfaces, a pathway involving C-C coupling and diamine formation through reductive elimination of an intermediate Co(II) alkyl species is preferred. Co thin films with an average thickness of 10 - 25 nm obtained from the process are subjected to thorough analysis comprising AFM, SEM, RBS/NRA as well as depth profiling XPS. Resistivity measurements for ~ 22 nm thick films grown on a defined SiO₂ insulator layer yield highly promising values in a range of 15 - 20 μΩ cm without any after treatment.

Tunable Split-Disk Metamaterial Absorber for Sensing Application

We present four designs of tunable split-disk metamaterial (SDM) absorbers. They consist of a bottom gold (Au) mirror layer anchored on Si substrate and a suspended-top SDM nanostructure with one, two, three, and four splits named SDM-1, SDM-2, SDM-3, and SDM-4, respectively. By tailoring the geometrical configurations, the four SDMs exhibit different tunable absorption resonances spanning from 1.5 µm to 5.0 µm wavelength range. The resonances of absorption spectra can be tuned in the range of 320 nm, and the absorption intensities become lower by increasing the gaps of the air insulator layer. To increase the sensitivity of the proposed devices, SDMs exhibit high sensitivities of 3312 nm/RIU (refractive index unit, RIU), 3362 nm/RIU, 3342 nm/RIU, and 3567 nm/RIU for SDM-1, SDM-2, SDM-3, and SDM-4, respectively. The highest correlation coefficient is 0.99999. This study paves the way to the possibility of optical gas sensors and biosensors with high sensitivity.

Simulation of a Charged Al2O3 Film As An Assisting Passivation Layer For a-Si Passivated Contact p-Type Silicon Solar Cells

In this paper, a charged Al2O3 tunneling film as an assisting for amorphous Si (a-Si) passivated contact layer is proposed and theoretically simulated for its potential application in improving a-Si passivated contact p-type (a-PC-p) solar cell. The concept is based on an Ag/n+ c-Si/p c-Si/Al2O3/p+ a-Si/Al structure. The key feature is the introduction of a charged Al2O3 layer, which facilitates the tunneling of holes through an Al2O3 insulator layer accompanied by the reduction of interface defect density (Dit). The negative charge in the Al2O3 layer makes the energy band of p-type c-Si bend upward, realizing the accumulation of holes and repelling of electrons at the c-Si/a-Si interface simultaneously. The influence of interface negative charges (Qit) between a-Si and c-Si, Al2O3 thickness, Al2O3 bandgap, interface defect density (Dit) at the a-Si/c-Si interface are systematically investigated on the output parameters of a-PC-p cells. Inserting a charged Al2O3 film between the c-Si/a-Si interface, a +4.2 % relative efficiency gain is predicted theoretically compared with the a-PC-p cells without the Al2O3 layer. Subsequently, the device performance under various temperatures is simulated, and the insertion of a charged Al2O3 layer obviously decreases the Pmax temperature coefficient from -0.336 % /℃ to -0.247 % /℃, which is analogous to that of Heterojunction with Intrinsic Thin layer (HIT) solar cell. The above results demonstrate a better temperature response for a-PC-p cells with a charged Al2O3 layer, paving a road for its potential application in high-efficiency and high thermal stability a-PC-p solar cells.