Papers by Keyword: Deep Level

Abstract: SiC devices such as MOSFETs and SBDs reduce power loss in fast-switching condition as compared to Si devices. However, shallow and deep levels in SiC significantly affect dynamic characteristics of SiC devices. We already reported that high densities of deep levels were discovered in Al⁺-implanted samples other than the shallow Al acceptor level. In this work, we applied the deep level to the TCAD simulation, and examined the behavior of the carriers at high dV/dt conditions.

Abstract: The deep levels ON₁ and ON_2a/b introduced by oxidation into 4H-SiC are characterized via standard DLTS and via filling pulse dependent DLTS measurements. Separation of the closely spaced ON_2a/b defect is achieved by using a higher resolution correlation function (Gaver-Stehfest 4) and apparent energy level, apparent electron capture cross section and filling pulse measurement derived capture cross sections are given.

Abstract: We investigated annealing behavior of the carrier lifetime and the deep levels in electron irradiated n-type and semi-insulating 4H-SiCs. We observed two peaks for each sample by photo induced current transient spectroscopy (PICTS) measurements, and their heights depended on annealing temperature. By comparing the annealing behavior of the peak height with reported temperature dependence of concentrations of various defects, we speculated that the observed peaks originate from either V_SiV_C, C_SiV_C or EI4.

Abstract: We have characterized deep levels in as-grown and electron irradiated p-type 4H-SiC epitaxial layers by the current deep-level transient spectroscopy (I-DLTS) method. A part of the samples were irradiated with electrons in order to introduce defects. As a result, we found that electron irradiation to p-type 4H-SiC created complex defects including carbon vacancy or interstitial. Moreover, we found that observed deep levels are different between before and after annealing, and thus annealing may change structures of defects.

Abstract: Using the peculiar behavior of nitrogen molecules in FZ silicon crystals contained with a high concentration of vacancies, this paper describes the following four important values: the estimated vacancy concentrations, the deep levels at 0.44 eV under the conduction band for n-type and at 0.66 eV over the valence band for p-type for mono vacancies and the diffusion coefficient of the silicon interstitials DI-FZ = 1.3×exp(-4.5 eV/kT).

Abstract: The temperature dependences of the piezoelectric photo-thermal (PPT) signals from unintentionally doped p-type GaAsN films grown on semi-insulating GaAs substrate were measured from 80 to 300 K. From the theoretical analysis based on the rate equation for the recombination of photo exited carriers to the localized levels, we identified five majority hole traps, P1-P5 in GaAsN films. Among them, estimated concentrations of the P3 and P5 traps increased with the nitrogen contents. Therefore, we concluded that these two traps were due to nitrogen-related recombination centers in GaAsN.

Abstract: We demonstrated high-speed imaging of photoluminescence (PL) and electroluminescence (EL) for not only band-to-band but also multiple deep-level emissions in a multicrystalline Si solar cell. We used a cooled InGaAs camera with a photosensitive range of 900 - 1700 nm equipped with band-pass filters for the selective detection of various deep-level emissions. The exposure time for imaging was only 1 - 10 seconds. Comparisons of the present PL images with the microscopic PL mappings confirmed for us that essentially the same luminescence patterns were obtained.

Abstract: The floor heave is one of soft rock roadway distortion. Based on soft rock supporting theory and engineering practice, the program bolt-mesh-anchors and floor corner, bolts coupling support to control floor heave of the soft rock roadway is proposed. Numerical simulation results show that bolt-anchors can mobilize the strength of the deep adjacent rock, at the same time, and properly arranged floor corner bolts with high bending rigidity can cut the slip-line field and achieve the goal of controlling floor heave effectively.

Abstract: The electrical properties of the SiO₂/SiC interface fabricated by sodium-enhanced oxidation (SEO) of n-type 4H-SiC were studied by temperature-dependent C-V and constant-capacitance deep level transient spectroscopy (CCDLTS). With the exception of near-interface traps in the SiC epi-layer, which are not present in the SEO samples, the trap species observed in SEO capacitors are the same as those observed in both standard-oxidized and NO-annealed MOS capacitors. Total electron trapping in accumulation is comparable in SEO and NO-annealed capacitors; however, the traps in SEO capacitors are located at the interface whereas tunneling into oxide traps is observed in NO-annealed samples. A series of bias-temperature stress tests show that electron trapping is essentially unchanged when mobile sodium ions are moved toward the interface. The improved mobility attained by this process compared to NO annealing may be due to the absence of near-interface SiC traps in SEO samples.

Abstract: It has been clarified that Z_1/2 center, a well known deep level as a lifetime killer, can be reduced to the concentration below 10¹¹ cm^-3 by thermal oxidation or C⁺ implantation plus Ar annealing. In this study, the authors investigate the trap-reduction phenomena systematically (experimentally), and propose a model to analyze the phenomena. Furthermore, prediction of the defect distributions is realized by solving a diffusion equation in accordance with the trap reduction model. This analytical model can explain almost all experimental data: oxidation-temperature dependence, oxidation-time dependence, and initial-Z_1/2-concentration dependence of the defect reduction. Based on these results, the authors accomplish to eliminate the Z_1/2 center to a depth of 100 μm in the sample with a relatively high initial-Z_1/2-concentration of 10¹³ cm^-3 by thermal oxidation at 1400°C for 16.5 h.