| 1. |
- Hallén, Anders., et al.
(author)
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Annealing of Al implanted 4H silicon carbide
- 2006
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In: Physica Scripta. - 0031-8949 .- 1402-4896. ; T126, s. 37-40
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Journal article (peer-reviewed)abstract
- Al ions were implanted with multiple energies up to 250 keV at elevated temperatures in n-type 4H SiC epitaxial layers to reach a surface concentration of 1 x 10(20) cm(-3). These samples were then annealed at temperatures between 1500 and 1950 degrees C. A similar 4H SiC epitaxial sample was implanted by MeV Al ions to lower doses and annealed only at 200 and 400 degrees C. After annealing, cross-sections of the samples were characterized by scanning spreading resistance microscopy (SSRM). The results show that the resistivity of high-dose Al implanted samples has not reached a saturated value, even after annealing at the highest temperature. For the MeV Al implanted sample, the activation of Al has not yet started, but a substantial annealing of the implantation induced damage can be seen from the SSRM depth profiles.
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| 2. |
- Sandberg, Åke, 1944-, et al.
(author)
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DN Debatt : Ett hållbart arbetsliv kräver medbestämmande
- 2016
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In: Dagens Nyheter. - Stockholm : Bonnier. - 1101-2447.
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Journal article (pop. science, debate, etc.)abstract
- REPLIK. Arbetsmiljöverket ser information som lösningen på arbetsmiljöproblemen. Och ibland räcker information, men inte när intressen är delvis motstridiga. Ska arbetslivet bli hållbart krävs stärkt inflytande för skyddsombud och de anställdas och fackets medbestämmande i frågor om sättet att organisera och styra arbetet, skriver fyra forskare.
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| 3. |
- Sandberg, Åke, et al.
(author)
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Prioritera forskning om att organisera för hälsa i arbetet
- 2016
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In: Universitetsläraren. - 0282-4973.
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Journal article (pop. science, debate, etc.)abstract
- Organisationsforskning om och för bra arbetsplatser faller mellan stolarna. Det hävdar sex forskare inom olika ämnen, som nu föreslår en rad övergripande förändringar. Bland annat ett eget forskningsråd för arbetslivsforskning.
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| 4. |
- Suchodolskis, A., et al.
(author)
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Ion implantation damage annealing in 4H-SiC monitored by scanning spreading resistance microscopy
- 2006
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In: Thin Solid Films. - : Elsevier BV. - 0040-6090 .- 1879-2731. ; 515:2, s. 611-614
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Journal article (peer-reviewed)abstract
- To obtain a better understanding of the damage annealing process and dopant defect incorporation and activation we have implanted epitaxially grown 4H-SiC layers with high doses of Al+ ions. Cross-sections of the samples are investigated by scanning spreading resistance microscopy (SSRM) using a commercial atomic force microscopy (AFM). The defects caused by the implanted ions compensate for the doping and decrease the charge carrier mobility. This causes the resistivity to increase in the as-implanted regions. The calculated profile of implanted ions is in good agreement with the measured ones and shows a skewed Gaussian shape. Implanted samples are annealed up to 400 degrees C. Despite these low annealing temperatures we observe a clear improvement of the sample conductivity in the asimplanted region.
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| 5. |
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| 6. |
- Österman, John, 1971-
(author)
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Characterization of electrical properties in 4H-SiC by imaging techniques
- 2004
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Doctoral thesis (other academic/artistic)abstract
- 4H-SiC has physical properties supremely suited for a variety of high power, high frequency and high temperature electronic device applications. To fully take advantage of the material's potential, several problems remain to be solved. Two of the most important are (1) the characterization and understanding of crystallographic defects and their electrical impact on device performance, and (2) the introduction of acceptor dopants, their activation and control of the final distribution of charge carriers. Two main experimental methods have been employed in this thesis to analyze 4H-SiC material with respect to the issues (1) and (2): electron beam induced current (EBIC) and scanning spreading resistance microscopy (SSRM), respectively. EBIC yields a map of electron-hole-pairs generated by the electron beam of a scanning electron microscope and collected in the depleted region around a junction. EBIC is conducted in two modes. In the first mode the EBIC contrast constitutes a map of minority carrier diffusion lengths. Results from these measurements are compared to white beam syncrotron x-ray topography and reveal a one-to-one correlation between lattice distortions and the electron diffusion length in n+p 4H-SiC diodes. In the second EBIC mode, the junction is highly reverse biased and local avalanche processes can be studied. By correlating these EBIC results with other techniques it is possible to separate defects detrimental to device performance from others more benign. SSRM is a scanning probe microscopy technique that monitors carrier distributions in semiconductors. The method is for the first time successfully applied to 4H-SiC and compared to alternative carrier profiling techniques; spreading resistance profiling (SRP), scanning electron microscopy (SEM) and scanning capacitance microscopy (SCM). SCM successfully monitors the doping levels and junctions, but none of these techniques fulfill the requirements of detection resolution, dynamic range and reproducibility. The SSRM current shows on the other hand a nearly ideal behavior as a function of aluminum doping in epitaxially grown samples. However, the I-V dependence is highly non-linear and the extremely high currents measured indicate a broadening of the contact area and possibly an increased ionization due to sample heating. Finite element calculations are performed to further elucidate these effects. SSRM is also applied to characterize Al implantations as a function of anneal time and temperature. The Al doping profiles are imaged on cleaved cross-sections and the measured SSRM current is integrated with respect to depth to obtain a value of the total activation. The evaluation of the annealing series shows a continuous increase of the activation even up to 1950 °C. Other demonstrated SSRM applications include local characterization of electrical field strength in passivating layers of Al2O3, and lateral diffusion and doping properties of implanted boron.
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