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成果報告書詳細
管理番号20180000000110
タイトル*平成29年度中間年報 エネルギー・環境新技術先導プログラム 未踏チャレンジ2050 AINを用いたヘテロ接合型超高耐圧・大電流パワーデバイスとAIN結晶評価技術の開発
公開日2018/12/27
報告書年度2017 - 2017
委託先名一般財団法人ファインセラミックスセンター 国立大学法人山口大学
プロジェクト番号P14004
部署名イノベーション推進部
和文要約
英文要約This research has two main goals (A-1) Development of evaluation techniques for AlN single crystal, and (B-1) Growth of high quality AlN crystal and fabrication of AlN-based power device".

(A-1)The goal of A-1 is to establish a low-cost evaluation technique that can fastly reveal crystal defects in large-area single-crystal AlN, including their types, density and distribution.
In A-1, crystal quality of AlN single-crystal was evaluated from both Al- and N-polar faces by using high-resolution X-ray diffraction. Synchrotron X-ray topography (XRT) was carried out with diffraction vectors of g=11-26 (asymmetric), g=1-106 (asymmetric) and g=0006 (symmetric), to reveal and categorize dislocations across the whole wafer with diameter of 20~30 millimeters in a nondestructive way. Dislocations were also investigated by using chemical etching based on molten KOH solution with Na2O2 additive. Dislocations under the etch pits were picked up in the form of 150-thick slab (TEM specimen) by using focused ion beam (FIB) equipment. Structures of dislocations were observed by means of TEM. By applying weak-beam condition, burgers vectors of dislocations can be judged by g.b criterion.

(B-1) Study of a growth of N-polar AlN and N-polar GaN/AlN HFET

In B-1, we proposed the N-polar GaN/AlN HFET to achieve high two-dimensional electron gas (2DEG), high breakdown voltage and high electron mobility. First of all, the simulation of the novel this structure was carried out to confirm the realization of the HEMT characteristics. As a result, it was found that high 2DEG can be obtained using the novel structure and high drain current also can be expected, which value is as three times as higher than that of conventional AlGaN/GaN HEMT. To achieve the N-polar GaN/AlN HFET, high-quality N-polar AlN and strained GaN on it is essential. It was found that N-polar AlN should be grown by optimizing growth temperature and V/III ratio and N-polar GaN is easily relaxed due to large lattice mismatch between GaN and AlN and it is important to optimize the growth conditions.

(Summary)
In the FY2017, commerically-available high quality AlN single-crystal wafer was used to evaluate AlN quality and to establish dislocation revelation techniques. By performing XRD, synchrotron XRT and chemical etching, we have successfully reveal dislocations in AlN and categorize them into several types according to their burgers vectors. On the other hand, novel HFET device structure was proposed to achieve 2DEG, and growth condition necessary for high quality N-face AlN growth was investigated.
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