Емкостная спектроскопия гетероэпитакиальных AlGaAs/GaAs p-i-n-структур

Temperature dependences of capacitance-voltage (C−V) characteristics and deep-level spectra of the graded highvoltage AlxGa1−xAs p0 −i−n0 junction grown by liquid-phase epitaxy via autodoping with background impurities were investigated. The changes of the C−V characteristics at varied measurement temperature and optical illumination demonstrated that the p0-, i-,n0-type layers in the AlxGa1−xAs under study contain bistable DX centers. In spectra of deep-level transient spectroscopy (DLTS), measured at various bias voltages Vr and filling pulses Vf , a positive DLTS peak is observed for the n 0 -type layer with thermal activation energy Et = 280 meV and electron-capture cross-section σn = 3.17 · 10−14 cm2, which is unusual for a majority-carrier trap. This peak is related to the negatively charged state of the Se/Te donor impurity, which is a bistable DX center with negative correlation energy U.

Effect of nuclear deformation on electron capture cross-section on chromium isotopes

The electron capture plays significant role in the presupernova and supernova evolutions of massive stars which in turn are of great importance in synthesizing heavy elements beyond iron. In this paper, we study the effect of nuclear deformation on the computed electron capture cross-section on selected even–even chromium isotopes ([Formula: see text]Cr). The nuclear deformation parameters were computed using two different theoretical models: Interacting Boson Model (IBM-1) and Macroscopic (Yukawa-plus-exponential)–microscopic (Folded–Yukawa) model (Mac–mic model). A third value of deformation parameter was adopted from experimental data. We chose the pn-QRPA model to perform our calculations. The predictive power of the chosen model was first tested by calculating Gamow–Teller (GT) strength distributions of selected [Formula: see text]-shell nuclei where measured GT data was available. The calculated GT strength distributions were well-fragmented over the energy range 0–12[Formula: see text]MeV and were noted to be in decent agreement with experimental data. The total GT strength was found to increase (decrease) with decrease (increase) in the value of deformation parameter for the three chromium isotopes. The computed GT strength distributions satisfied the model-independent Ikeda sum rule. The ECC were calculated as a function of the deformation parameter at core temperature 1.0[Formula: see text]MeV. Our results show that the calculated ECC increased with increasing value of nuclear deformation.

The Study of Deep Level Traps and Their Influence on Current Characteristics of InP/InGaAs Heterostructures

The damage mechanism of proton irradiation in InP/InGaAs heterostructures was studied. The deep level traps were investigated in detail by deep level transient spectroscopy (DLTS), capacitance–voltage (C–V) measurements and SRIM (the stopping and range of ions in matter, Monte Carlo code) simulation for non-irradiated and 3 MeV proton-irradiated samples at a fluence of 5 × 1012 p/cm2. Compared with non-irradiated samples, a new electron trap at EC-0.37 eV was measured by DLTS in post-irradiated samples and was found to be closer to the center of the forbidden band. The trap concentration in bulk, the interface trap charge density and the electron capture cross-section were 4 × 1015 cm−3, 1.8 × 1012 cm−2, and 9.61 × 10−15 cm2, respectively. The deep level trap, acting as a recombination center, resulted in a large recombination current at a lower forward bias and made the forward current increase in InP/InGaAs heterostructures for post-irradiated samples. When the deep level trap parameters were added into the technology computer-aided design (TCAD) simulation tool, the simulation results matched the current–voltage measurements data well, which verifies the validity of the damage mechanism of proton irradiation.

Collision dynamics of proton to water dimer at 250 eV

Applying a real-space, real-time implementation of time-dependent density functional theory coupled to molecular dynamics (TDDFT-MD) non-adiabatically, we study the ionization and fragmentation of water dimer in collision with a proton at 250 eV. Four different incident orientations with various impact parameters are employed to account for orientation effects. The reaction channels, electronic density evolution, scattering pattern and energy loss of proton are obtained. We find that proton is scattered away for all impact parameters and the head-on collision effects the energy loss of proton dominantly as well as the scattering angle. The locations of peaks of the scattering angles are similar to those corresponding to the energy loss. The single-electron capture, the double-electron capture as well as the total electron capture cross-sections are obtained. We find that the single-electron capture cross-section contributes most to the total electron capture cross-section and the calculated total electron capture cross-section is in reasonable agreement with experimental and other theoretical results with respect to water gas and liquid water.

Conductance Signal from Near-Interface Traps in n-Type 4H-SiC MOS Capacitors under Strong Accumulation

We find a clear correlation between the density of near-interface traps (NITs) in n-type 4H-SiC MOS capacitors and the strength of a conductance signal observed under strong accumulation. The conductance signal strength can be described by tunneling of electrons between the SiC conduction band and NITs at a rate close to the ac test signal frequency. The findings here show that the signal in dry thermal oxides depends on temperature which suggests that the electron capture cross section of the NITs is thermally activated. Direct tunneling is more prominent in samples containing low density of NITs such as oxides made by sodium enhanced oxidation (SEO).