| 研究実績の概要 |
The thermal phonon transportation in superlattices has been investigated. Using metal organic chemical vapor deposition, high-quality InGaN/GaN superlattices, AlGaN/GaN superlattices are prepared. The interface is very sharp into nanometer level by transmission electron microscopy. By changing period thickness in superlattics, the crossover from incoherent to coherent phonon transport were determined. It is found that, when the period thickness is lower than phonon mean free path, coherent phonon transport was achieved. The thickness is also influenced by the quality, such as dislocations in superlattices. At the high-density interface, the coherence starts to be disturbed due to larger strain and degraded interface morphology. Moreover, highly orientated polycrystalline diamond film was deposited on GaN template by micro-plasma chemical vapor deposition.The diamond film has a thermal conductivity approaching 250W/mK when the thickness is ~1 um, belonging to the high level for polycrystalline diamond film. The optimized superlattices were introduced as interlayer between GaN and diamond as the thermal dissipation solution. The thermal boundary resistance was achieved as low as 4m2K/GW, which is much lower than those with SiNx of AlN interlayers.
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| 今後の研究の推進方策 |
We will further optimize the interface of superlattices by MOCVD, to reduce the interface defects in InAlN/GaN and AlGaN/AlN superlattices. The measurement and analysis of the thermal property across interface will be necessary. Furthermore, theoretical calculation on phonon transport is also important
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