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首页> 外文期刊>Journal of Physics, D. Applied Physics: A Europhysics Journal >Epitaxial growth and optical properties of Al- and N-polar AlN films by laser molecular beam epitaxy
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Epitaxial growth and optical properties of Al- and N-polar AlN films by laser molecular beam epitaxy

机译：激光分子束外延外延生长Al和N极性AlN薄膜的光学性能

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摘要

Epitaxial aluminum nitride (AlN) films with c-axis orientation were grown on both (1 1 1) MgO and c-sapphire substrates by laser molecular beam epitaxy. The in-plane epitaxial relationships were determined to be [1 1 2-bar 0]AlN||[0 1-bar 1]MgO and [1 1-bar 0 0]AlN||[1 1 2-bar 0]sapphire, and the lattice mismatch was 4.2% and 13.2% for AlN films on MgO and sapphire, respectively. The AlN films were shown to be Al- and N-polar on MgO and sapphire, respectively. The former is assumed to be caused by the centre of inversion symmetry of (1 1 1) MgO substrate, while the latter is due to the O polarity of sapphire. The full-width at half-maximum of the ω-scanning spectrum for AlN film on (1 1 1) MgO substrate is smaller than that on the c-sapphire substrate. The optical band-gap energies for AlN films grown on MgO and sapphire were found to be 5.93 and 5.84 eV, close to the standard band gap of 6.2 eV, and the calculated Urbach energies were 0.27 eV and 0.53 eV, respectively. These results indicate a lower amorphous content and/or less defects/impurities in Al-polar than N-polar AlN.
机译：通过激光分子束外延在（1 1 1）MgO和c-蓝宝石衬底上生长具有c轴取向的外延氮化铝（AlN）膜。面内外延关系确定为[1 1 2-bar 0] AlN || [0 1-bar 1] MgO和[1 1-bar 0 0] AlN || [1 1 2-bar 0]蓝宝石，MgO和蓝宝石上的AlN膜的晶格失配分别为4.2％和13.2％。 AlN膜在MgO和蓝宝石上分别显示为Al和N极性。假定前者是由（1 1 1）MgO衬底的反转对称中心引起的，而后者则是由蓝宝石的O极性引起的。在（1 1 1）MgO衬底上的AlN膜的ω-扫描光谱的半峰全宽小于c-蓝宝石衬底上的AlN膜的全宽。发现在MgO和蓝宝石上生长的AlN薄膜的光学带隙能量为5.93和5.84 eV，接近标准带隙6.2 eV，计算出的Urbach能量分别为0.27 eV和0.53 eV。这些结果表明，与N极的AlN相比，Al极的无定形含量低和/或缺陷/杂质少。

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