| 1. |
- Kalinina, E., et al.
(författare)
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Structural, electrical, and optical properties of low-doped 4H-SiC chemical vapor deposited epitaxial layers
- 2001
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 90:10, s. 5402-5409
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Tidskriftsartikel (refereegranskat)abstract
- Results of complex studies of structural, optical, and electrical characteristics of 4H-SiC n-type low-doped epitaxial layers grown by the chemical vapor deposition (CVD) method are presented. Characteristics of CVD layers grown on commercial wafers with and without a thin (<0.1 mum) buffer layer grown by liquid phase epitaxy (LPE) between the commercial wafer and CVD epitaxial layer were compared. It has been shown that the LPE filling process caused a significant improvement in the structural quality of CVD layers. Cathodoluminescence (CL) data and electrical characteristics of Schottky barriers (SB) revealed that the LPE layer also made the concentration profiles of the uncompensated donors and recombination centers for holes as well as the hole diffusion lengths more uniform over the CVD layer. According to CL and secondary ion mass-spectroscopy measurements the presence of aluminum as an impurity was detected in initial commercial wafers, as well as having LPE and CVD epitaxial layers. Forward current-voltage characteristics of SBs formed on CVD layers with and without a LPE buffer layer followed an exponential relationship with an ideality factor of 1.04-1.06 over six to seven orders of magnitude in current density. A noticeable increase of the breakdown voltage was also observed in samples with a LPE layer.
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| 2. |
- Laube, M., et al.
(författare)
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Electrical activation of high concentrations of N+ and P+ ions implanted into 4H-SiC
- 2002
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 92:1, s. 549-554
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Tidskriftsartikel (refereegranskat)abstract
- Comparative Hall effect investigations are conducted on N- and P-implanted as well as on (N+P)-coimplanted 4H-SiC epilayers. Box profiles with three different mean concentrations ranging from 2.5x10(18) to 3x10(20) cm(-3) to a depth of 0.8 mum are implanted at 500 degreesC into the (0001)-face of the initially p-type (Al-doped) epilayers. Postimplantation anneals at 1700 degreesC for 30 min are conducted to electrically activate the implanted N+ and P+ ions. Our systematic Hall effect investigations demonstrate that there is a critical donor concentration of (2-5)x10(19) cm(-3). Below this value, N- and P-donors result in comparable sheet resistances. The critical concentration represents an upper limit for electrically active N donors, while P donors can be activated at concentrations above 10(20) cm(-3). This high concentration of electrically active P donors is responsible for the observed low sheet resistance of 35 Omega/square, which is about one order of magnitude lower than the minimum sheet resistance achieved by N implantation.
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| 7. |
- Kalinina, E., et al.
(författare)
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Material quality improvements for high voltage 4H-SiC diodes
- 2001
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Ingår i: Materials Science & Engineering. - 0921-5107 .- 1873-4944. ; 80:03-jan, s. 337-341
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Tidskriftsartikel (refereegranskat)abstract
- The influence of thin 4H-SiC buffer layers grown by liquid phase epitaxy (LPE) on structural quality of 4H-SiC low-doped epitaxial layers, grown by chemical vapor deposition (CVD) was investigated in detail. A dramatic defect density reduction in CVD epitaxial layers grown on commercial wafers with buffer LPE layer was detected. P(+)n junctions were formed on these CVD layers by high dose Al ion implantation followed by rapid thermal anneal. It was shown that both the increase of diffusion lengths of minority carriers (Lp) in CVD lavers and the forming of p(+)-layers after Al ion implantation and high temperature anneal lead to superior device characteristics.
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| 8. |
- Schoner, A., et al.
(författare)
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Dependence of the aluminium ionization energy on doping concentration and compensation in 6H-SiC
- 1996
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Ingår i: Silicon Carbide and Related Materials1995. - : Institute of Physics Publishing (IOPP). - 0750303352 ; , s. 493-496
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Konferensbidrag (refereegranskat)abstract
- Hall-effect measurements on aluminium (Al)-doped p-type 6H-SiC were made and the dependence of the Al ionization energy on doping concentration and compensation was investigated. It is shown that the Al ionization energy is almost constant for a degree of compensation K much less than 0.01 up to an Al concentration of 5 . 10(20)cm(-3). An average value for the Al ionization energy is found to be 241.6 +/- 5.2 meV. Additionally, we find that the Al ionization energy for a degree of compensation in a range of 0.01 to 0.5 varies with doping concentration and compensation. An impurity band model describing this dependence is discussed.
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