Ge nano-belts with large tensile strain are considered as one of the promising materials for high carrier mobility metal- oxide-semiconductor transistors and efficient photonic devices. In this paper, we design the Ge nano-belts on an insulator surrounded by Si3N4 or SiO？ for improving their tensile strain and simulate the strain profiles by using the finite difference time domain （FDTD） method. The width and thickness parameters of Ge nano-belts on an insulator, which have great effects on the strain profile, are optimized. A large uniaxial tensile strain of 1.16% in 50-nm width and 12-nm thickness Ge nano-belts with the sidewalls protected by Si3N4 is achieved after thermal treatments, which would significantly tailor the band gap structures of Ge-nanobelts to realize the high performance devices.
Well-aligned and closely-packed silicon nanopillar （SNP） arrays are fabricated by using a simple method with magnetron sputtering of Si on a porous anodic alumina （PAA） template at room temperature. The SNPs are formed by selective growth on the top of the PAA pore walls. The growth mechanism analysis indicates that the structure of the SNPs can be modulated by the pore spacing of the PAA and the sputtering process and is independent of the wall width of the PAA. Moreover, nanocrystals are identified by using transmission electron microscopy in the as-deposited SNP samples, which are related to the heat isolation structure of the SNPs. The Raman focus depth profile reveals a high crystallization ratio on the surface.
We report a lateral Ge-on-Si ridge waveguide light emitting diode （LED） grown by ultrahigh vacuum chemical vapor deposition （UHV-CVD）. Direct-bandgap electroluminescence （EL） of Ge waveguide under continuous current is observed at room temperature. The heat-enhancing luminescence and thermal radiation-induced superlinear increase of edge output optical power are found. The spontaneous emission and thermal radiation based on the generalized Planck radiation law are calculated and fit very well to the experimental results. The Ge waveguides with different lengths are studied and the shorter one shows stronger EL intensity.
在Si(001)衬底上,以高质量的弛豫Ge薄膜作为缓冲层,先后生长Sn组分x分别为2.5%,5.2%和7.8%的完全应变的三层Ge_(1-x)Sn_x合金薄膜.在Si(001)衬底上直接生长了x分别为0.005,0.016,0.044,0.070和0.155的五个弛豫Ge_(1-x)Sn_x样品.通过卢瑟福背散射谱、高分辨X射线衍射和X射线倒易空间图等方法测量了Ge_(1-x)Sn_x合金的组分与晶格常数.实验得到的晶格常数相对Vegard定律具有较大的正偏离,弯曲系数b=0.211 A.
