Trap Density Energy Research Articles

Structural and electrical characterizations of nanocrystalline Zn1−xCdxS (0≤x≤0.9) prepared by low cost dip coating

Thin films of nanocrystalline Zn1−xCdxS (0≤x≤0.9) were deposited by a dip coating method on glass substrates from aqueous solution containing cadmium acetate, zinc acetate and thiourea at 200°C. The morphological, structural and electrical properties of the deposited Zn1−xCdxS thin films were studied by atomic force microscopy (AFM), X-ray diffractometer (XRD), selected area electron diffraction (SAED) and photoluminescence (PL). To understand the predominant conduction mechanism of the nanocrystalline Zn1−xCdxS (0≤x≤0.9) thin films, DC electrical conductivity was measured in the temperature range of 300–420K. These measurements revealed that the DC behavior of the films can be described by a one-dimensional variable range hopping (VRH) model in the entire temperature range instead of a three-dimensional variable range hopping (VRH) model. The current density–voltage (J–V) characteristics of Zn1−xCdxS (0≤x≤0.9) thin films shows that the current conduction is ohmic type at the low-voltage region while the charge transport phenomenon appears to be space charge limited current (SCLC) at the higher-voltage regions. The latter conduction is attributed to the presence of a discrete trapping level. Various electrical parameters were determined and studied as a function of Cd-content such as electron mobility (μ0), density of states in conduction band (Nc), Fermi energy (EF), trap energy (Et) and trap electron density (Nt).

Reliability of High-Mobility InGaAs Channel n-MOSFETs Under BTI Stress

The reliability performance of InxGa1-xAs n-MOSFETs with Al2O3 gate dielectric under positive-bias temperature instability stress is investigated. The following new phenomena are demonstrated: 1) There are high densities of fast interface traps Nit and slow oxide border traps NSOX near the interface between InGaAs and Al2O3. The border traps are more fragile under stress, and therefore, the stress mainly induces border traps. 2) The stress-induced border traps consist of permanent acceptor traps and recoverable donor traps. Acceptor trap energy density ΔDSOXAcceptor(E) is mainly distributed above the conduction band edge Ec of InGaAs with a tail extending to the midgap, whereas donor trap energy density ΔDSOXDonor(E) has a large distribution inside the InGaAs energy gap with a tail extending to the conduction band. 3) Flicker noise variation after stress and its correlation to the acceptor and donor trap generation and recovery are demonstrated. 4) The recoverable donor traps induce the subthreshold slope and off-current degradation in the stress phase and recover in the recovery phase and also induce continuous degradation of on-current in the recovery phase. The permanent acceptor traps induce the transconductance and on-current degradation. The long-term device lifetime is mainly determined by the generation rate of the acceptor traps. 5) Comprehensive comparison between the Si and InGaAs MOSFETs' degradation behaviors under bias temperature instability stress is presented. The physical recovery of donor oxide traps in dielectric in InGaAs/Al2O3 has never been observed in a Si MOS structure, deserving special attention and further investigation.

Effect of electrical and thermal stressing on charge traps in XLPE cable insulation

Insulation peelings were taken from a single 90 kV ac transmission cable whose segments had been stressed for between ~8000 and 10 000 h either at elevated temperature (363 K) or field 19.5 kV/mm (rms) (T= 293 K). Control peelings were taken from a cable segment that had experienced no stressing. The various peelings were subjected to an endurance test at 70 kV/mm (rms) and T = 363 K, which demonstrated that only those peelings that had experienced thermal stressing had a reduced lifetime compared to the set of control peelings. Space charge measurements made prior to the endurance test showed only negative space charge in all types of peelings and an analysis of the decay dynamics in the control set showed that it resided in two trap distributions at 0.8 to 0.9 eV and 1 to ~1.5 eV. Peelings from a second endurance test (55 kV/mm (rms), T = 363 K) were suspended when the test was terminated at 6088 h. Space charge measurements showed that these samples exhibited positive as well as negative space charge with the positive charge being ~60% of the total. The space charge decay dynamics also showed two trap distributions, ~0.65eV to 0.85 eV and 1eV to ~1.3 eV, with both positive and negative charge in each energy range. Detailed differences in the trap energy range and density in both distributions were found between peelings with different cable histories, and those differences that correlate with a reduction of endurance life are identified. A tentative explanation in terms of anti-oxidant consumption and trap generation by chemical reaction is proffered.

The Effect of Annealing on the Transient Deuterium Permeation Characteristics of Tungsten

Effect of annealing on the transient permeation behavior of deuterium implanted into pure tungsten was investigated. Permeation experiment was carried out with pure tungsten foils (34 mm in diameter, 25 micro-m in thickness, and 99.5% purity) annealed at 1273 K for 3 hours in vacuum and unannealed one. Those permeation characteristics at transient state were analyzed by TMAP4 code. As a result, the feature of the trap site in the unannealed tungsten specimen was revealed that which has about 0.9 eV trap energy and 40ppm-trap density. By the analysis of the permeation behavior through the annealed tungsten, above trap sites disappeared by specimen annealing, and the permeation through annealed tungsten was found to be expressed by simple diffusion equation with the effective diffusion coefficient. However, it may involve the trapping parameter, which is virtually indistinguishable from reduction of diffusion coefficient, in itself.

The fractional thermoluminescence: some aspects concerning the experimental data analysis

Abstract The data analysis method of the fractional glow technique (FGT) is revised once more. A new method for the determination of the trap energy density spectrum for first-order kinetics is proposed. Application of this method to the analysis of experimental and simulated data are presented. The necessity of careful control of both the heating and cooling during the FGT procedure is stressed.