Impact of nitridation on structural and optical properties of MOVPE-grown m-plane GaN layers on LiAlO2
Impact of nitridation on structural and optical properties of MOVPE-grown m-plane GaN layers on LiAlO2
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氮化对 LiAlO2 上 MOVPE 生长的 m 面 GaN 层的结构和光学性能的影响
DOI：
10.1002/pssc.200880790
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通讯作者：
R. H. Jansen
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作者：
C. Mauder;L. Rahimzadeh Khoshroo;H. Behmenburg;B. Reuters;M. Bösing;M. V. Rzheutskii;E. V. Lutsenko;G. P. Yablonskii;J. F. Woitok;M. M. C. Chou;M. Heuken;H. Kalisch;R. H. Jansen
本文研究了LiAlO 2衬底的氮化对金属有机物气相外延（MOVPE）生长m面（1 - 100）GaN层的影响。在薄膜沉积之前，我们通过将晶片暴露于NH3达在无预处理和300 s之间的不同时间来进行原位衬底预处理。随后生长的层的性质显示出显着的依赖于此氮化步骤。我们发现，这一过程对于获得纯m面GaN薄膜至关重要，并且对X射线摇摆曲线（XRC）半峰全宽（FWHM）值具有有益的影响，该值降低了近两个数量级。用NH3预处理的沉积层也表现出更光滑的表面，均方根（RMS）粗糙度值从1.20 nm降低到1.66 nm。此外，氮化大大增加了GaN的室温（RT）光致发光（PL）光谱的带边发射强度。此外，我们比较了衬底对水的敏感性，未涂覆的LiAlO 2晶片与不氮化过程。虽然未处理的表面在浸入去离子（DI）水中5分钟时显示出明显的粗糙化，但我们可以看到对氮化基材表面没有显著影响。这表明表面组成发生了变化，从而保护了敏感的衬底表面，并为高质量m面GaN薄膜的成核提供了良好的条件。（© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA，魏因海姆）
In this paper, we investigate the influence of the nitridation of LiAlO2substrates on the growth of m‐plane (1‐100) GaN layers by metal‐organic vapour phase epitaxy (MOVPE). Before thin film deposition, we performed an in‐situ substrate pretreatment by exposing the wafer to NH3for different times between no pretreatment and 300 s. The properties of subsequently grown layers show a significant dependency on this nitridation step. We find that this procedure is essential for obtaining pure m‐plane GaN films and has a beneficial effect on the X‐ray rocking curve (XRC) full width at half maximum (FWHM) value, which decreases by almost two orders of magnitude. Deposited layers with NH3pretreatment also exhibit much smoother surfaces with a reduction of the root mean square (RMS) roughness value from ∼20 to ∼6 nm. Additionally, the nitridation greatly increases the GaN band edge emission intensity in room temperature (RT) photoluminescence (PL) spectroscopy. Furthermore, we compare the sensitivity of the substrate against water for uncoated LiAlO2wafers with and without nitridation process. While the untreated surface shows a clear roughening when dipped into de‐ionized (DI) water for 5 min, we can see no significant impact on the nitridated substrate surface. This indicates a change in surface composition which protects the sensitive substrate surface and provides good conditions for the nucleation of high‐quality m‐plane GaN films. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)