Cathodoluminescence study of h– and c–GaN single crystals grown by a Na or K flux
Cathodoluminescence study of h– and c–GaN single crystals grown by a Na or K flux
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Na 或 K 助熔剂生长的 h- 和 c-GaN 单晶的阴极发光研究
DOI：
10.1016/s1468-6996(02)00003-7
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发表时间：
2002
影响因子：
5.5
通讯作者：
M. Shimada
中科院分区：
文献类型：
--
作者：
T. Sekiguchi;H. Yamane;M. Aoki;T. Aoki;M. Shimada
用阴极射线发光光谱研究了六方（h-）和立方（c-）GaN自支撑单晶的发光特性。在750 ℃下，通过Ga和N2在Na助熔剂中的反应合成了尺寸约为0.2-2 mm的h-GaN晶体，而在K助熔剂中合成了尺寸约为0.3mm或更小的c-GaN晶体。与以NaN 3为氮源生长的晶体相比，h-GaN在室温下表现出较强的带边发射。在20 K时，h-GaN的带边发射分裂为四个峰。主要能量峰位置为3.478 eV，其被指定为无A激子发射。c-GaN的主峰的能量位置为3.268 eV。假设h-GaN和c-GaN中激子的结合能分别为25和26 meV，则h-GaN和c-GaN之间的带隙能量差估计为209 meV。由于这些晶体不受来自衬底的应变的影响，因此峰值能量对于本征GaN晶体是可靠的。c-GaN的半峰全宽比h-GaN的宽得多，表明立方相比六方相更有缺陷。
Luminescence properties of hexagonal (h-) and cubic (c-) GaN freestanding single crystals were studied by means of cathodoluminescence spectroscopy. The h-GaN crystals of about 0.2–2 mm in dimension were synthesized at 750 C by the reaction of Ga and N 2 in a Na flux, while c-GaN crystals of about 0.3 mm or less in a K flux. The h-GaN showed rather strong band edge emission at room temperature compared with the crystal grown by using NaN 3 as a nitrogen source. At 20 K, the band edge emission of h-GaN was split into four peaks. The main energy peak position was 3.478 eV, which was assigned as the A-free exciton emission. The energy position of the main peak of c-GaN was 3.268 eV. Assuming the binding energies of excitons in h-and c-GaN as 25 and 26 meV, respectively, the energy difference of bandgap between h-and c-GaN is estimated to be 209 meV. Since these crystals are free from strain from the substrates, the peak energies are reliable for the intrinsic GaN crystals. The full widths at half maximum of the emission of c-GaN were much broader than those of h-GaN, suggesting that the cubic phase is much defective compared with the hexagonal one.