Pushan Guha Roy , Sayantani Sen , Chirantan Singha , Anirban Bhattacharyya
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引用次数: 0
摘要
通过等离子体辅助分子束外延(PA-MBE)生长出了具有极高 AlN 分子分数(∼ 90 %)的 AlGaN 合金,并通过高分辨率 X 射线衍射(HR-XRD)测量研究了其合金特性。生长过程采用了一系列 III/V 族比,对于在高 III 族条件下生长的样品,合金中的相分离从 HR-XRD 图形中 AlGaN (0002) 峰的特征性分裂中显而易见。随着 III 族过量条件的降低,峰位置的分离不断减小,直至观察到单一峰。然而,对于不存在这种分离的样品,在 XRD 图样的较低入射角处可以看到自发的超晶格峰,这表明存在长程原子有序(LRAO)。因此,对于铝含量极高的 AlGaN 合金,根据生长动力学的不同,可以观察到相分离或 LRAO 的影响。这些关于相分离效应的研究结果有望通过载流子在电位极小值处的定位过程,减轻位错和相关非辐射重组中心的有害影响,从而促进高效深紫外发射器的开发,达到皮肤安全杀菌的目的。
Growth of AlGaN alloys with ∼ 90 % AlN mole fraction by plasma-assisted molecular beam epitaxy: Indication of phase-segregation effects
AlGaN alloys with very high AlN mole fraction (∼90 %) were grown by plasma-assisted molecular beam epitaxy (PA-MBE) and their alloy properties were investigated by high-resolution X-ray diffraction (HR-XRD) measurements. Growth was carried out employing a series of group III/V ratios and for samples grown under a high group-III regime, phase-segregation in the alloy was evident from a characteristic splitting of the AlGaN (0002) peak in the HR-XRD pattern. With decreasing excess group-III conditions the separation of peak positions continuously reduced, till a single peak was observed. However, for samples where such splitting was absent, spontaneous superlattice peaks were seen at lower incident angles of the XRD patterns indicating the presence of long-range atomic ordering (LRAO). Thus, for AlGaN alloys with extremely high Al content, effects of phase-segregation, or of LRAO were observed, depending on the kinetics of growth. These results on phase-segregation effects are expected to promote the development of high-efficiency deep ultraviolet emitters for skin-safe germicidal action by mitigating the detrimental effect of dislocations and related non-radiative recombination centers through carrier localization processes at potential minima.
期刊介绍:
The journal offers a common reference and publication source for workers engaged in research on the experimental and theoretical aspects of crystal growth and its applications, e.g. in devices. Experimental and theoretical contributions are published in the following fields: theory of nucleation and growth, molecular kinetics and transport phenomena, crystallization in viscous media such as polymers and glasses; crystal growth of metals, minerals, semiconductors, superconductors, magnetics, inorganic, organic and biological substances in bulk or as thin films; molecular beam epitaxy, chemical vapor deposition, growth of III-V and II-VI and other semiconductors; characterization of single crystals by physical and chemical methods; apparatus, instrumentation and techniques for crystal growth, and purification methods; multilayer heterostructures and their characterisation with an emphasis on crystal growth and epitaxial aspects of electronic materials. A special feature of the journal is the periodic inclusion of proceedings of symposia and conferences on relevant aspects of crystal growth.