| 1. |
- David, M. L., et al.
(författare)
-
Electrically active defects in irradiated 4H-SiC
- 2004
-
Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 95:9, s. 4728-4733
-
Tidskriftsartikel (refereegranskat)abstract
- 4H-SiC epilayers were irradiated with either protons or electrons and electrically active defects were studied by means of deep level transient spectroscopy. Motion of defects has been found to occur at temperature as low as 350-400 K. Indeed, the application of an electric field has been found to enhance modifications in defect concentrations that can also occur during long time annealing at elevated temperature. Two levels have been revealed and labeled B and M. Two other levels, referred to as S-1 and S-2 and located at 0.40 and 0.71 eV below the conduction band edge have been studied in detail (capture cross sections, profiling, formation energy, activation energy during annealing). The S-1 and S-2 levels have been found to exhibit a one to one relation and are proposed to be two charge states of the same acceptor center, labeled the S center.
|
|
| 2. |
- Martin, David M., et al.
(författare)
-
Bistable defect in mega-electron-volt proton implanted 4H silicon carbide
- 2004
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 84:10, s. 1704-1706
-
Tidskriftsartikel (refereegranskat)abstract
- Epitaxial 4H-SiC n-type layers implanted at room temperature with a low fluence of mega-electron-volt protons have been measured by deep level transient spectroscopy (DLTS). The proton fluence of 1x10(12) cm(-2) creates an estimated initial concentration of intrinsic point defects of about 10(14) cm(-3) of which about 10% remain after the implantation and gives rise to deep states in the upper part of the band gap. Here, we investigate the samples prior to high-temperature annealing and a very complex spectrum is revealed. In particular, a bistable defect M is discovered having two DLTS peaks, M-1 and M-3 at E-C-0.42 and around E-C-0.75 eV, respectively, in one configuration and one peak, M-2 at E-C-0.70 eV in the other configuration. The charge dependent thermal activation energies for the transformation between the bistable defect peaks are 0.90 and 1.40 eV.
|
|
| 3. |
- Monakhov, E. V., et al.
(författare)
-
Laplace transform transient spectroscopy study of a divacancy-related double acceptor centre in Si
- 2003
-
Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 15:39, s. S2771-S2777
-
Tidskriftsartikel (refereegranskat)abstract
- Radiation-induced divacancy-related levels in high-purity oxygen-enriched n-type silicon have been studied with the use of deep level transient spectroscopy (DLTS) and Laplace-DLTS. It has been shown that heat treatment at 250degreesC results in a shift of the divacancy (V-2)-related peaks observed by 'standard' DLTS. Using Laplace-DLTS it is demonstrated that the shift is due to annealing of V-2 and formation of a new acceptor centre. The new centre has presumably two negative charge states: singly and doubly negative. The formation of the new centre holds a close one-to-one correlation with the annealing of V-2, indicating that the new centre is a result of divacancy interaction with an impurity or a defect. The close position of the electronic levels of the new centre to that of V-2 suggests a similar electronic and microscopic structure of the new centre to V-2, and a tentative identification is a divacancy-oxygen centre.
|
|
| 4. |
- Svensson, B. G., et al.
(författare)
-
Defects and diffusion in high purity silicon for detector applications
- 2004
-
Ingår i: Conference on Photo-Responsive Materials, Proceedings. - : Wiley-VCH Verlagsgesellschaft. - 3527405526 ; , s. 2250-2257
-
Konferensbidrag (refereegranskat)abstract
- In this contribution we review some recent results on defects occurring after irradiation and thermal treatment of silicon detectors for ionizing radiation. In particular, the annealing of the prominent divacancy centre and the concurrent growth of a new double acceptor centre, assigned to the divacancy-oxygen pair, is treated in detail. The detectors were fabricated using oxygenated high purity float zone (FZ) silicon wafers of n-type in order to improve the radiation hardness. The results obtained have important implication on our current understanding of the degradation of silicon detectors at high radiation fluences and suggest that a new concept for optimised impurity/defect engineering needs to be developed.
|
|
| 5. |
- Paturzo, M., et al.
(författare)
-
Investigation of electric internal field in congruent LiNbO3 by electro-optic effect
- 2004
-
Ingår i: Applied physics letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 85, s. 5652-5654
-
Tidskriftsartikel (refereegranskat)abstract
- We investigate the effect of the defect-induced internal field on the electro-optic behavior of z-cut congruent lithium niobate crystals. We measure, by a spatially resolved interferometric technique, the phase retardation due to an external applied voltage occurring in two regions with opposite ferroelectric polarization. When measurements are performed just after electrical poling, the two opposite domains show a different electro-optic behavior. We interpret this as due to an elastic component of the internal field. In fact, the asymmetric behavior disappears when the sample is thermally annealed, i.e., when the internal field vanishes
|
|
