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首页> 外文期刊>Journal of Applied Physics >Compositional inhomogeneities in AlGaN thin films grown by molecular beam epitaxy: Effect on MSM UV photodetectors
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Compositional inhomogeneities in AlGaN thin films grown by molecular beam epitaxy: Effect on MSM UV photodetectors

机译：通过分子束外延生长的AlGaN薄膜中的成分不均匀性：对MSM紫外光电探测器的影响

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Ultraviolet (UV) MSM photodetectors (PD) based on AlGaN alloys find many applications, including flame sensing. In this work we investigate the dependence of AlGaN based photodetectors grown by MBE on the kinetics of growth. MSM photodetectors were fabricated in the interdigitated configuration with Ni/Au contacts having 400 μm finger length and 10μm finger spacing. Bulk Al_(0.4)Ga_(0.6)N films were grown on to sapphire substrates using an AlN buffer layer. A series of PDs were developed using the Al_(0.4)Ga_(0.6)N films grown under different group Ⅲ/Ⅴ flux ratios ranging from stoichiometric conditions to much higher than unity. Upon testing, it was observed that the otherwise identical photodetectors show significant decrease in dark current as AlGaN deposition conditions change from stoichiometric to excess group Ⅲ, due to reduction of unintentional incorporation of oxygen-related point defects. In addition, the intensity and spectral dependence of the photocurrent also change, showing an extended low energy tail for the former and a sharp and prominent excitonic peak for the latter. The optical transmission measurements indicate a variation in Urbach energy with deposition conditions of the AlGaN films, although they have the same absorption edge. While all samples show a single red-shifted photoluminescence peak at room temperature, upon cooling, multiple higher energy peaks appear in the photoluminescence (PL) spectra, indicating that the alloys contain complex compositional inhomogeneities. Two types of alloy fluctuations, determined by the growth conditions, have been identified that modulate the optoelectronic properties of AlGaN by changing the spatial localization of excitons, thereby altering their stability. We identified that growth under stoichiometric conditions leads to compositional inhomogeneities that play a detrimental role in the operation of MSM photodetectors, which reduces the sharpness of the sensitivity edge, while growth under excess metal conditions enhances it.
机译：基于AlGaN合金的紫外线（UV）MSM光电探测器（PD）有许多应用，包括火焰感应。在这项工作中，我们研究了MBE生长的基于AlGaN的光电探测器对生长动力学的依赖性。 MSM光电探测器以指状配置制造，其中Ni / Au触点的手指长度为400μm，手指间距为10μm。使用AlN缓冲层将块状Al_（0.4）Ga_（0.6）N膜生长到蓝宝石衬底上。利用在不同的Ⅲ/Ⅴ族通量比范围（从化学计量条件到远大于1）生长的Al_（0.4）Ga_（0.6）N膜，开发了一系列PD。经测试，观察到，由于减少了无意识地掺入与氧有关的点缺陷，当AlGaN沉积条件从化学计量改变为过量的Ⅲ组时，其他方面相同的光电探测器显示出暗电流显着降低。另外，光电流的强度和光谱依赖性也改变，对于前者显示出扩展的低能量尾巴，而对于后者显示出尖锐且突出的激子峰。光学透射率测量结果表明，尽管AlGaN膜具有相同的吸收边，但它们的Urbach能量随AlGaN膜沉积条件的变化而变化。尽管所有样品在室温下均显示单个红移光致发光峰，但冷却后，在光致发光（PL）光谱中会出现多个更高的能量峰，表明合金包含复杂的成分不均匀性。已经确定了由生长条件决定的两种类型的合金涨落，它们通过改变激子的空间定位来调节AlGaN的光电性能，从而改变其稳定性。我们发现，在化学计量条件下的生长会导致成分不均匀，在MSM光电探测器的操作中起有害作用，这会降低灵敏度边缘的清晰度，而在过量金属条件下的生长会增强灵敏度。

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  • 来源
    《Journal of Applied Physics》 |2016年第14期|144502.1-144502.9|共9页
  • 作者

    Pallabi Pramanik; Sayantani Sen; Chirantan Singha; Abhra Shankar Roy; Alakananda Das; Susanta Sen; A. Bhattacharyya;

  • 作者单位

    Centre for Research in Nanoscience and Nanotechnology, University of Calcutta, Kolkata 700106, India;

    Centre for Research in Nanoscience and Nanotechnology, University of Calcutta, Kolkata 700106, India;

    Centre for Research in Nanoscience and Nanotechnology, University of Calcutta, Kolkata 700106, India;

    Centre for Research in Nanoscience and Nanotechnology, University of Calcutta, Kolkata 700106, India;

    Institute of Radio Physics and Electronics, University of Calcutta, Kolkata 700009, India;

    Institute of Radio Physics and Electronics, University of Calcutta, Kolkata 700009, India;

    Institute of Radio Physics and Electronics, University of Calcutta, Kolkata 700009, India;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);
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