High reflectivity and broad bandwidth AlN/GaN distributed Bragg reflectors grown by molecular-beam epitaxy
High reflectivity and broad bandwidth AlN/GaN distributed Bragg reflectors grown by molecular-beam epitaxy
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DOI：
10.1063/1.126483
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发表时间：
2000-05-15
影响因子：
4
通讯作者：
Chu, SNG
中科院分区：
文献类型：
--
作者：
Ng, HM;Moustakas, TD;Chu, SNG
利用电子回旋共振等离子体辅助分子束外延技术，在（0001）蓝宝石上生长了许多基于AlN/GaN四分之一波层的分布式Bragg反射器（dbr）。dbr的周期数在20.5 ~ 25.5之间，四分之一波层的厚度选择使得反射率峰值出现在近紫外到绿色波长区域。这些dbr的峰值反射率值在97% ~ 99%之间。最佳样品的峰值反射率高达99%，中心为467 nm，带宽为45 nm。将该样品的实验反射率数据与透射矩阵法的模拟数据进行了比较，结果表明，在峰值反射率、高反射率带宽和旁瓣位置方面，该样品的反射率数据非常吻合。通过透射电镜证实了四分之一波层的厚度和均匀的周期性。在一些样品中观察到网络裂纹，这归因于AlN层中的拉伸应力。我们制备了具有较厚AlN层和较薄GaN层的非对称dbr，以降低AlN层的抗拉强度。这样的方法导致样品的裂缝明显减少，甚至没有裂缝。(C) 2000年美国物理研究所。[s0003 - 6951(00) 00820 - 2]。
A number of distributed Bragg reflectors (DBRs) based on AlN/GaN quarterwave layers have been grown on (0001) sapphire by electron cyclotron resonance plasma-assisted molecular-beam epitaxy. The number of periods for the DBRs ranges from 20.5 to 25.5 and the thickness of the quarterwave layers were chosen such that the peak reflectance occurs from the near ultraviolet to green wavelength regions. Peak reflectance values between 97% and 99% were obtained for these DBRs. The best sample has a peak reflectance up to 99% centered at 467 nm with a bandwidth of 45 nm. The experimental reflectance data for this sample were compared with simulations using the transmission matrix method and show excellent agreement with respect to peak reflectance, bandwidth of high reflectance, and the locations of the sidelobes. The thickness of the quarterwave layers and uniform periodicity of the bilayers were confirmed by cross-section transmission electron microscopy. A network of cracks was observed in some of the samples and this is attributed to tensile stress in the AlN layers. We have grown asymmetric DBRs with thicker AlN layers and thinner GaN layers to reduce the tensile strength in the AlN layers. Such an approach resulted in samples that have significantly less cracks or even crack-free. (C) 2000 American Institute of Physics. [S0003-6951(00)00820-2].