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幸运快三赔率多少: 生長溫度對使用激光MBE在a-平面藍寶石上制備的外延GaN薄膜的結構和光學性質的影響

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發表于 2018-5-31 09:09:04 | 只看該作者 回帖獎勵 |倒序瀏覽 |閱讀模式
Influence of growth temperature on structural and optical properties of laser MBE grown epitaxial thin GaN films on a-plane sapphire
生長溫度對使用激光MBE在a-平面藍寶石上制備的外延GaN薄膜的結構和光學性質的影響
Journal of Vacuum Science & Technology B 36, 04G102 (2018);

https://doi.org/10.1116/1.5025126

Chodipilli Ramesh and Prashant Tyagi
  CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110012, India and Academy of Scientific and Innovative Research, CSIR-NPL Campus, Dr. K. S. Krishnan Road, New Delhi 110012, IndiaSandeep Singh and Preetam Singh
  CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110012, IndiaGovind Gupta, Kamlesh Kumar Maurya, Kuchibhotla Murali Krishna Srivatsa, Muthusamy Senthil Kumar, and Sunil Singh Kushvahaa)
  CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110012, India and Academy of Scientific and Innovative Research, CSIR-NPL Campus, Dr. K. S. Krishnan Road, New Delhi 110012, India
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a)Author to whom correspondence should be addressed; electronic mail: [email protected]

ABSTRACT
摘要

Epitaxial thin GaN films (~60 nm) have been grown on a-plane sapphire substrates at different growth temperatures (500–700 °C) using laser molecular beam epitaxy (LMBE). The effect of growth temperatures on the structural and optical properties of GaN layers grown on low temperature (LT) GaN buffer on prenitridated a-sapphire have been studied systematically. The in situ reflection high energy electron diffraction pattern revealed the three-dimensional epitaxial growth of GaN films on a-sapphire under the adopted growth conditions. The full width at half maximum (FWHM) value of x-ray rocking curves (XRCs) along GaN (0002) and (10-12) planes decreases with increasing growth temperature. The FWHM values of (0002) and (10-12) XRC for the 700 °C grown GaN film are 1.09° and 1.08°, respectively. Atomic force microscopy characterization showed that the grain size of GaN increases from 30–60 to 70–125 nm with the increase in growth temperature as GaN coalescence time is shorter at high temperature. The refractive index value for the dense GaN film grown at 600 °C is obtained to be ~2.19 at the wavelength of 632 nm as deduced by spectroscopic ellipsometry. Photoluminescence spectroscopy confirmed that the epitaxial GaN layers grown on a-sapphire at 600–700 °C possess near band edge emission at ~3.39 eV, close to bulk GaN.
The GaN growth at 700 °C without a buffer still produced films with better crystalline and optical properties, but their surface morphology and coverage were inferior to those of the films grown with LT buffer. The results show that the growth temperature strongly influences the structural and optical quality of LMBE grown epitaxial GaN thin films on a-plane sapphire, and a growth temperature of >600 °C is necessary to achieve good quality GaN films.


        使用激光分子束外延(LMBE)在不同生長溫度(500-700℃)下在a平面藍寶石襯底上生長了外延薄GaN膜(約60nm)。作者系統地研究了生長溫度對生長在低溫(LT)GaN緩沖層上的GaN層的結構和光學性質的影響,該GaN緩沖層是沉積在經過預氮化的a-藍寶石上。原位反射高能電子衍射圖案揭示了在所采用的生長條件下在a-藍寶石上的GaN薄膜的三維外延生長。沿著GaN(0002)和(10-12)平面的X射線搖擺曲線(XRCs)的半峰全寬(FWHM)值隨著生長溫度的增加而降低。在700 °C下生長的GaN膜的(0002)和(10-12)XRC的FWHM值分別為1.09°和1.08°。原子力顯微鏡的表征表明,隨著生長溫度的增加,GaN的晶粒尺寸從30-60增加到70-125nm,這是因為在高溫下GaN聚結時間較短。由光譜橢偏儀推導出,在600 °C下生長的致密GaN膜的折射率值在632nm波長處為約2.19。光致發光光譜證實,在600-700℃在a-藍寶石上生長的外延GaN層在〜3.39eV附近具有近帶邊發射,接近體材料GaN。沒有緩沖層的700 °C下生長的GaN仍然能產生具有更好結晶性和光學性質的膜層,但是其表面形態和覆蓋度低于使用了LT緩沖層生長的薄膜。所得的結果表明,生長溫度對在平面藍寶石上使用LMBE生長的外延GaN薄膜的結構和光學性質有很大影響,生長溫度 >600 °C對于獲得高質量的GaN薄膜是必要的條件。


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