| 1. |
- Gluba, L., et al.
(författare)
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On the nature of the Mn-related states in the band structure of (Ga,Mn)As alloys via probing the E-1 and E-1 + Delta(1) optical transitions
- 2014
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 105:3
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Tidskriftsartikel (refereegranskat)abstract
- The dilute (Ga,Mn)As became a model ferromagnetic semiconductor, however there is still a disagreement on the source of its magnetism. In this paper, we verify the ellipsometric results and compare them with more precise photoreflectance method, which gives an important insight into the interaction of the Mn-related states with the ones of GaAs valence band. No spectral shifts observed for the E-1 and E-1 + Delta(1) interband transitions in highly doped and annealed (Ga,Mn)As epitaxial layers indicate that the coupling between a detached Mn impurity band and the valence band does not occur. Our findings are supported by the characterizations of the (Ga,Mn)As epitaxial layers with the high resolution transmission electron microscopy and magnetization measurements. (c) 2014 AIP Publishing LLC.
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| 2. |
- Desmaris, Vincent, 1977, et al.
(författare)
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Surface Engineering for high efficiency GaN HEMTs
- 2011
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Ingår i: Proceeedings of the 7th international Workshop on Semiconductor Surface Passivation, 11-15 Sept. 2011, Krakow, Poland.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- High Electron Mobility Transistors (HEMT) based on III-Nitrides have demonstrated excellent microwave performance as power transistors, owing to the large bandgaps of the materials they are as made of, as well as the high band offset and high electron mobility observed in the AlGaN/GaN heterojunctions. Nevertheless, the microwave performance of GaN HEMTs is still largely determined by their surface condition due to the inherent high polarization fields present in their epistructure. Such performance degradation mechanisms are often referred as Gate-lag.In this paper, different surface engineering approaches for mitigating negative surface influence on the device performance are investigated. Different passivation materials, dielectric deposition methods, device fabrication technique and epistructure (GaN Cap layers) device (recess) have been studied for the optimization of GaN device performances. As a result, optimized structures have demonstrated about 6 W/mm and 10 W/mm of CW output power density for GaN HEMTs grown on sapphire and SiC respectively.
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