Imajo Toshifumi, Suemasu Takashi, Toko Kaoru
Institute of Applied Physics, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8573, Japan.
JSPS Research Fellow, 8 Ichiban-cho, Chiyoda-ku, Tokyo, 102-8472, Japan.
Sci Rep. 2021 Apr 15;11(1):8333. doi: 10.1038/s41598-021-87616-x.
Polycrystalline Ge thin films have attracted increasing attention because their hole mobilities exceed those of single-crystal Si wafers, while the process temperature is low. In this study, we investigate the strain effects on the crystal and electrical properties of polycrystalline Ge layers formed by solid-phase crystallization at 375 °C by modulating the substrate material. The strain of the Ge layers is in the range of approximately 0.5% (tensile) to -0.5% (compressive), which reflects both thermal expansion difference between Ge and substrate and phase transition of Ge from amorphous to crystalline. For both tensile and compressive strains, a large strain provides large crystal grains with sizes of approximately 10 μm owing to growth promotion. The potential barrier height of the grain boundary strongly depends on the strain and its direction. It is increased by tensile strain and decreased by compressive strain. These findings will be useful for the design of Ge-based thin-film devices on various materials for Internet-of-things technologies.
多晶锗薄膜因其空穴迁移率超过单晶硅片且工艺温度较低而受到越来越多的关注。在本研究中，我们通过调制衬底材料，研究了在375°C下通过固相结晶形成的多晶锗层的应变对其晶体和电学性能的影响。锗层的应变范围约为0.5%（拉伸）至 -0.5%（压缩），这既反映了锗与衬底之间的热膨胀差异，也反映了锗从非晶到晶体的相变。对于拉伸应变和压缩应变，由于生长促进作用，大应变会产生尺寸约为10μm的大晶粒。晶界的势垒高度强烈依赖于应变及其方向。它会因拉伸应变而增加，因压缩应变而降低。这些发现将有助于设计用于物联网技术的各种材料上的锗基薄膜器件。
