GaAs/AlGaAs量子阱材料的X射线形貌及其发光性能

本文介绍了用X射线双品形貌术研究MBE生长的GaAs/AlGaAs量子阱材料中的生长缺陷、位错及其对发光性能的影响。同时研究了低温下MBE生长的GaAs/AlGaAs量子阱材料的正交方向的位错。在有应变超品格过渡层高温生长的量子阱材料中,位错及光致发光性能有明显的改善。

X-RAY TOPOGRAPHY AND PHOTOLUMINESCENCE PROPERTIES OF GaAs/AlGaAs QUANTUM WELL MATERIALS

GaAs/AlGaAs quantum well materials have been greatly improved for the optoelectronic devices applications. The purpose of this paper is to report the recent research results on the MBE heterojunction materials, using the methods of the X-ray topography and photoluminescence (PL).Double crystal X-ray diffractive technique is used to study the MBE growth GaAs/AlGaAs quantum well (QW) epitaxy layers with the X-ray topography. Defects and dislocations can be found from ths topography images, and it is shown that the quality of this MBE grouth QW materials is strongly related to the growth temperature and the interface properties. The uniformity of this QW materials can be improved greatly by choosing suitable temperature and growing strain superlattices between the substrate and the epitaxy layers. The general samples were grown at temperature of 580℃ and the improved ones were grown at 680℃ with eight strain superlattices layers. Some grown cross dislocations distributs the directions of 110] and 110], which are projected from the climed dislocations in the growth layers, can be observed in the general MBE samples with a high density. However, in only limited area of the improved samples, for example at the edge or corner, this kind of dislocations can be observed. On most of the area of this samples we can find the X-ray diffraction pattern which lefeis that the epitaxial crystal is fine both in. the uniformity and qualityy. Also, we can find that the stress profile of the improved sample is uniform, v. which cemes frcm the impr vement of the int rface qvality, and resulted from the free of the substrate defects.Lew temperature PL, at UK, is used to study the luminescence properties and the composition distribution in the samples. The PL intensity of the general samples is low due to the high density of dislocations. In the improved sample with strain superlattices. the P’L intensity is one hundred times higher than that in the general one, and we can see the high energy transitions from n=1 and n=2 of the QW confined effects. The PL intensity profile is greatly improved at the same time, which means good uniformity there.The Al composition of the heterojuncirn layer AlGaAs was studied by both the X-ray and PL measurements. A little difference can be found in both of the different growth samples. However, in the improved case, the Al composition difference in only in the order of 0.01 at whole wafer,at least only a half of that difference in the general case.Conclusion. The MBE growth GaAs/AlGaAs QW materials can be improved by the choice cf suitablle temperature and imrtion of a series strain superlat-tices layers between substrate and the epitaxy Layers. X- ray topography and PL are both very useful in the diagnosis of the teterojvr.ction crystals to study the dislocation distribution, inteiface propeities and uniformity without damaging sample.