Efforts to improve carrier mobility in radio frequency sputtered aluminum doped zinc oxide films
Efforts to improve carrier mobility in radio frequency sputtered aluminum doped zinc oxide films
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DOI：
10.1063/1.1641524
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发表时间：
2004-02-15
影响因子：
3.2
通讯作者：
Wuttig, M
中科院分区：
文献类型：
--
作者：
Agashe, C;Kluth, O;Wuttig, M
研究了射频磁控溅射铝掺杂氧化锌（ZnO：Al）薄膜的电学和光学性质。主要的焦点是提高载流子迁移率μ，以同时实现对可见光和特别是近红外光的高透明度和低电阻率。研究了靶材中Al浓度、薄膜厚度、溅射功率、沉积气压和衬底温度对材料性能的影响。采用X射线衍射、二次离子质谱（西姆斯）、室温霍尔效应测量和光谱光度法分别研究了其结构、组成、电学和光学性质。所有ZnO：Al薄膜均为多晶，且沿[002]方向沿着择优取向。晶粒尺寸沿着生长方向随着Al掺杂的增加和薄膜厚度的增加而增加。西姆斯测量结果表明，薄膜中的Al浓度与靶中的Al浓度几乎相同。载流子浓度N和迁移率μ由目标Al浓度确定。此外，μ受膜厚度和溅射压力的影响。对于每个Al浓度，最高的mu通常在低沉积压力下观察到。通过使用具有0.5wt%的低Al 2 O3浓度的靶，μ可以提高到44.2 cm（2）/V s，同时保持电阻率ρ低至3.8 × 10（-4）Ω cm。对于这些膜，在近红外波长范围内的透明度显著提高，这使得它们对于光电器件如薄膜太阳能电池中的应用特别感兴趣。在不同条件下沉积的膜的μ-N依赖性进行了研究，以确定μ的实际限制。(C)2004年，美国物理学会。
This study addresses the electrical and optical properties of radio frequency magnetron sputtered aluminum doped zinc oxide (ZnO:Al) films. The main focus was on the improvement in carrier mobility mu to achieve simultaneously high transparency for visible and particularly near-infrared light and low resistivity. The influence of Al concentration in the target, film thickness, sputter power, deposition pressure, and substrate temperature on material properties was investigated. The structural, compositional, electrical and optical properties were studied using x-ray diffraction, secondary ion mass spectrometry (SIMS), room temperature Hall effect measurements and spectral photometry, respectively. All ZnO:Al films were polycrystalline and preferentially oriented along [002]. The grain size along the direction of growth increased with higher Al doping and with increasing film thickness. The SIMS measurements revealed that the Al concentration in the film was nearly the same as in the target. Carrier concentration N and mobility mu are determined by the target Al concentration. In addition mu is influenced by the film thickness and the sputter pressure. For each Al concentration, the highest mu was generally observed at low deposition pressures. By using a target with low Al2O3 concentration of 0.5 wt %, mu could be improved up to 44.2 cm(2)/V s while maintaining the electrical resistivity rho as low as 3.8x10(-4) Omega cm. For these films the transparency in the near-infrared wavelength range strongly improved which makes them particularly interesting for the application in optoelectronic devices like thin-film solar cells. The mu-N dependence for films deposited under diverse conditions was studied to identify a practical limit for mu. (C) 2004 American Institute of Physics.