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高质量的Si/SiGe异质结薄膜材料在集成电路和半导体量子计算等领域都有重要的应用。本研究工作首先通过分子束外延（MBE）在SOI衬底上获得上下Si层厚度一致的Si/SiGe/Si异质结；随后利用湿法刻蚀剥离该异质结，并接着刻蚀上下Si层，得到应力弛豫的SiGe薄膜；最后，将其转移到Si (001)衬底上并再次使用MBE在该转移SiGe薄膜上外延制备SiGe/Si/SiGe异质结。原子力显微镜表征显示异质结表面均方根粗糙度仅为0.118 nm，透射电镜和电子通道衬度成像均未观察到任何位错。研究显示基于转移SiGe薄膜上的Si/SiGe异质结完全消除了晶格失配引起的位错缺陷，为高性能的量子比特器件奠定了重要的材料基础。Strained silicon technology employing strain-relaxed SiGe virtual substrates has become pivotal for advancing Group IV semiconductor electronics, photonic devices, silicon-based quantum computing architectures, and neuromorphic devices. While existing approaches using Si/SiGe superlattice buffers and compositionally graded SiGe layers enable the fabrication of high-quality SiGe virtual substrates, defects including threading dislocations and crosshatch patterns still limit further performance enhancement. This study demonstrates a fabrication method for fully elastically relaxed SiGe nanomembranes that effectively suppresses the formation of both threading dislocations and crosshatch patterns. The fabrication process comprises three key steps: (1) epitaxial of Si/SiGe/Si heterostructures on silicon-on-insulator (SOI) substrates via molecular beam epitaxy (MBE); (2) fabrication of periodic pore arrays using photolithography and reactive ion etching (RIE); (3) selective wet etching and subsequent transfer of nanomembranes to Si (001) substrates. Subsequently, a Si/SiGe heterostructure was grown on the SiGe nanomembranes via MBE. The full elastic relaxation state of the SiGe nanomembranes and the fully strained state of the Si quantum well in the epitaxial Si/SiGe heterostructures were verified using Raman spectroscopy. Surface root-mean-square roughness values of 0.323 nm for the SiGe nanomembrane transferred to the silicon substrate and 0.118 nm for the epitaxial Si/SiGe heterostructure were demonstrated through atomic force microscopy (AFM) measurements. Uniform surface contrast in the Si/SiGe heterostructure grown on SiGe nanomembranes was demonstrated through electron channel contrast imaging (ECCI), with no detectable threading dislocations. Comparatively, the silicon substrate region exhibits a high density of threading dislocations accompanied by stacking faults. Crosssectional transmission electron microscope (TEM) analysis shows atomically sharp and defect-free interfaces. This research establishes a critical foundation for developing high-mobility two-dimensional electron gas systems and high-performance quantum bits.
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Keywords:
- Molecular Beam Epitaxy /
- Stress relaxation /
- SiGe /
- Heterojunction
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