Effect of epitaxial growth on electrical properties of Ga-doped ZnO thin films
Effect of epitaxial growth on electrical properties of Ga-doped ZnO thin films
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DOI：
10.1016/j.ceramint.2014.07.053
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发表时间：
2015
影响因子：
5.2
通讯作者：
Ji-Hong Kim;S. Koo
中科院分区：
文献类型：
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作者：
Ji-Hong Kim;S. Koo
研究了外延生长工艺对Ga掺杂ZnO（GZO）薄膜电学性能的影响。采用脉冲激光沉积（PLD）技术在Al 2 O3（0001）基片上生长了GZO薄膜.极图测量表明，GZO薄膜是相对于Al 2 O3（GZO [11 2 <$0]）面内旋转30°外延生长的||Al 2 O 3 [01 1 <$0]）以减少晶格失配。一个有趣的差异，衬底温度的电阻率的变化趋势相比，多晶GZO薄膜，这是为了比较，观察。多晶GZO的电阻率在200° C下降低，在400° C下略微降低，并且在600° C下突然增加。然而，外延GZO的电阻率在高达400° C时急剧下降，并且在600° C时继续下降。因此，在400和600° C的高温下获得低得多的结晶度。考虑到在每个温度下两种薄膜之间载流子浓度下降速率的差异很小，电阻率的这种不同趋势可以通过以下事实来解释：在高于200° C时外延GZO的霍尔迁移率的增加速率远高于多晶GZO的霍尔迁移率。高霍尔迁移率的外延GZO归因于高结晶度的外延生长，可以诱导较低的晶界散射。原子力显微镜（AFM）和高分辨X射线衍射仪（HRXRD）分析表明，与多晶GZO薄膜不同，在较高温度下生长的外延GZO薄膜具有较大的晶粒尺寸和较高的结晶度，即晶界散射可以降低得更多，霍尔迁移率即使在高温下也可以提高到足以补偿载流子浓度降低的程度。
The effect of epitaxial growth on the electrical properties of Ga-doped ZnO (GZO) thin films was studied. GZO thin films were grown on Al 2 O 3 (0001) substrates using pulsed laser deposition (PLD) at various substrate temperatures. Pole figure measurement revealed that the GZO films were grown epitaxially with a 30° in-plane rotation relative to Al 2 O 3 (GZO [11 2¯ 0]|| Al 2 O 3 [01 1¯ 0]) to reduce the lattice mismatch. An interesting difference in the variation trend of the resistivity by substrate temperature compared with that of the polycrystalline GZO films, which were prepared for comparison, was observed. The resistivity of the polycrystalline GZO decreased at 200° C, decreased slightly more at 400° C, and abruptly increased at 600° C. However, the resistivity of the epitaxial GZO decreased sharply at up to 400° C, and decreased continuously at 600° C. Consequentially, much lower resistivities were obtained at high temperatures of 400 and 600° C. Considering little difference in the rate of decrease in the carrier concentration between the two kinds of films at each temperature, this different tendency in the resistivity can be explained by the fact that the rate of increase in the Hall mobility of the epitaxial GZO at above 200° C is much higher than that of the polycrystalline GZO. The higher Hall mobility of the epitaxial GZO is attributed to high crystallinity caused by the epitaxial growth that can induce lower grain boundary scattering. It was proved by using an atomic force microscope (AFM) and a high resolution X-ray diffractometer (HRXRD) that the epitaxial GZO grown at higher temperature showed larger grain size and higher crystallinity, that is, the grain boundary scattering can decrease more, and the Hall mobility can increase enough to compensate for the decrease in the carrier concentration even at high temperature differently from the polycrystalline GZO films.