| 1. |
- Lankinen, A., et al.
(författare)
-
Dislocations at the interface between sapphire and GaN
- 2008
-
Ingår i: Journal of materials science. Materials in electronics. - : Springer Science and Business Media LLC. - 0957-4522 .- 1573-482X. ; 19:2, s. 143-148
-
Tidskriftsartikel (refereegranskat)abstract
- GaN layers grown by metal organic vapour phase epitaxy on sapphire were imaged by synchrotron radiation X-ray topography. The threading dislocations could not be resolved in the topographs due to their high density, but a smaller density of about 10(5) cm(-2) defects were seen in the interface between GaN and sapphire by utilizing large-area back-reflection topography for the sapphire substrates. The misfit dislocation images in the topographs form a well-resolved cellular network, in which the average cell size is roughly 30 mu m. Different cell shapes in the misfit dislocation networks are observed on different samples. Also, images of small-angle grains of similar size were found in transmission section topographs of the GaN layers.
|
|
| 2. |
|
|
| 3. |
- Jacobson, H., et al.
(författare)
-
Doping-induced strain in N-doped 4H-SiC crystals
- 2003
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 82:21, s. 3689-3691
-
Tidskriftsartikel (refereegranskat)abstract
- Stress in epitaxial layers due to crystal lattice mismatch directly influences the growth, structure, and basic electrophysical parameters of epitaxial films and also to a large extent the degradation processes in semiconductor devices. In this letter, we present a theoretical model for calculating the induced lattice compression due to N doping and the critical thickness concerning formation of misfit dislocations in homoepitaxial 4H–SiC layers with different N-doping levels. For example: The model predicts that substrates with a N concentration of 3×1019 cm-3 induce misfit dislocations when the epilayer thickness reaches ∼10 μm. Also, the N-doping concentration in the 1×1018–1×1019 cm-3 range yields a strain that not will cause misfit dislocactions at the substrate and epilayer interface until an epilayer thickness of 200–300 μm is reached. Supporting evidence of the induced lattice compression due to N doping have been done by synchrotron white-beam x-ray topography on samples with different N-doping levels and are compared with the predicted results from the model
|
|
| 4. |
- Jacobson, H., et al.
(författare)
-
Lateral enlargement of silicon carbide crystals
- 2004
-
Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248 .- 1873-5002. ; 270:1-2
-
Tidskriftsartikel (refereegranskat)abstract
- A new growth technique for lateral enlargement of silicon carbide crystals is presented and evaluated. The technique is based on PVT growth but modified with respect to temperature gradients and geometry as compared to conventional setup. Simulation of the temperature distribution for lateral growth as well as the growth mechanism is discussed. High-resolution X-ray diffraction and synchrotron white beam X-ray topography have been evaluated concerning structural defects. The results show that this growth technique makes it possible to enlarge seed crystals without threading screw dislocations and micropipes along the 0001 direction, but stacking faults are introduced due to the crystal stacking sequence along the <11¯00> directions. © 2004 Elsevier B.V.
|
|
| 5. |
- Jacobson, H., et al.
(författare)
-
Properties and origins of different stacking faults that cause degradation in SiC PiN diodes
- 2004
-
Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 95:3, s. 1485-1488
-
Tidskriftsartikel (refereegranskat)abstract
- Different properties of the reported stacking faults (SFs) and that both these types of SF are present in the material after electrical degradation of pin diodes are shown. One is caused by perfect dislocations, deflected or misfit dislocation that had dissociated into two partial dislocations. The partials are assumed to be close to each other with a separation below the detection limit of the SWBT measurements. Thus, enough energy is provided and the leading partial moves away from the other partial and forms the extended SF.
|
|
| 6. |
- Jacobson, Herbert, et al.
(författare)
-
Properties of different stacking faults that cause degradation in SiC PiN diodes
- 2003
-
Ingår i: Materials Science Forum, Vols. 433-436. ; , s. 913-916
-
Konferensbidrag (refereegranskat)abstract
- The electrical degradation of 4H-SiC PiN diodes has recently attracted a large interest and is a critical material problem for high power applications. The degradation is observed as an increased forward voltage drop after forward injection operation. In this paper we present the identity, properties and origin of stacking faults with different nature that cause degradation of 4H-SiC PiN diodes.
|
|
| 7. |
- Jacobson, H., et al.
(författare)
-
Structural impact of LPE buffer layer on sublimation grown 4H-SiC epilayers
- 2003
-
Ingår i: Journal of Crystal Growth. - 0022-0248 .- 1873-5002. ; 256:3-4, s. 276-282
-
Tidskriftsartikel (refereegranskat)abstract
- The objective of this work was to study the effect of a liquid phase epitaxy buffer layer on the development of defects in sublimation grown epitaxial layers of 4H-SiC. The results were analyzed with the aid of optical microscope, scanning electron microscope, high-resolution X-ray diffraction and synchrotron white beam X-ray topography. A pronounced effect of the liquid phase epitaxy buffer layer on formation of dislocations and micropipes is observed in the sublimation epitaxy layers. It has been shown that during sublimation growth of epilayer with a thin liquid phase epitaxy buffer layer (0.1µm) defects may undergo transformation and stacking faults can be formed. Sublimation grown epilayers grown on a thick liquid phase epitaxy buffer layer (1µm) also showed a symmetrical distribution of misfit dislocations along the <112¯0> and [11¯00] directions. © 2003 Elsevier B.V. All rights reserved.
|
|
| 8. |
- Jacobsson, Henrik, et al.
(författare)
-
High-resolution XRD evaluation of thick 4H-SiC epitaxial layers
- 2001
-
Ingår i: Materials Science Forum, Vols. 353-356. ; , s. 291-294
-
Konferensbidrag (refereegranskat)abstract
- 4H-SiC commercial wafers and sublimation grown epitaxial layers with a thickness of 100 mum have been studied concerning crystalline structure. The substrate wafers and the epitaxial layers have been separately investigated by high-resolution x-ray diffraction (HRXRD) and synchrotron white beam x-ray topography (SWBXT). The results show that the structural quality was improved in the epitaxial layers in the < 11 (2) over bar0 > and <(1) over bar 100 > directions, concerning domain distribution, lattice plane misorientation, mosaicity, and strain? compared with the substrates. Misoriented domains have merged together to form larger domains while the tilt between the domains was reduced, which resulted in non-splitting in diffraction curves. It is also clear that if the misorientation in the substrate gets too large, we can only see a slight decrease in the misorientation in the layer. At some positions on the substrates there were block structure (mosaicity). omega -rocking curves from epilayers at the same position showed smaller full width at half-maximum (FWHM) values and more uniform and narrow peaks. Curvature was almost the same in grown epilayers compared with the substrates. The shape of the grown epitaxial layers nas concave similarly to the substrates.
|
|
| 9. |
|
|
| 10. |
- Persson, Per, et al.
(författare)
-
Structural defects in electrically degraded 4H-SiC PiN diodes
- 2002
-
Ingår i: Materials Science Forum, Vols. 389-393. ; , s. 423-426
-
Konferensbidrag (refereegranskat)abstract
- Triangular structural defects, occasionally generated during long term operation of 4H-SiC pin diodes, are known to negatively affect the forward characteristics of the diode. We have used synchrotron white beam X-ray topography, scanning electron microscopy, in situ cathodo luminescence and transmission electron microscopy for characterizing the structure and formation mechanisms of such defects. It is shown from high-resolution images that the defect results from glide slip on the (0001) basal plane. The defect consists of a stacking fault bound by two partial dislocations with Burgers vectors 1/3<11 (1) over bar0> and 1/3<01 (1) over bar0>. The fault is a means for stress relaxation in the epilayer, near the contact layer using an existing dislocation as a nucleation source.
|
|
