Growth and Fundamental Properties of GeSi Bulk Crystals

锗硅(Ge_x；1-x&gt；Si_x或Ge-Si_xGe_&lt；1-x&gt；)合金是金刚石基固溶体中的一种完全互溶的固溶体，由于其具有带隙和晶格参数工程的潜力，在微电子和光电子器件方面引起了人们极大的兴趣。为了建立高质量的GeSi合金单晶的生长，阐明合金化所带来的各种基本性质，以及探索这种材料的本征性质和应用潜力的可能性，我们进行了这项研究：(1)用提拉法获得了成分为0&lt；x&lt；0.15和0.73&lt；x&lt；1的合金的大尺寸、直径大于25 mm、长度大于40 mm的完整单晶。重掺有电活性杂质的SiGe合金(0.80；x&lt；1)的单晶也被成功地获得。(2)XAFS研究…在局域原子结构上，Ge-Ge和Ge原子具有随机的取代位占据，但在整个成分范围内没有择优排列，Ge-Ge和Ge-Si键长在不完全Pauling情况下保持明显不同的长度，并随合金成分而线性变化。合金的机械强度在高温下变得对温度不敏感，并与成分成正比，在整个成分范围内与x(1-x)成正比，这可能源于与合金成分的微观波动和位错之间的动态相互作用有关的内应力场。(5)为了研制高温下可用的热电转换器，对重掺杂GeSi的电导、热导率和Seebeck系数进行了评估。较少

Germanium-silicon (Ge_<1-x>Si_x or Germanium-silicon Si_xGe_<1-x>) alloy is a fully miscible solid solution of the diamond-base and has attracted keen interest as material for both microelectronic and opto-electronic devices in view of the potential for band gap and lattice parameter engineering they offer. This research has been undertaken in order to establish the growth of high quality single crystals of GeSi alloys and to clarify the various fundamental properties that are brought about by alloying and the possibility of exploring the intrinsic properties and potentials of this material for wide applications.(1)Full single crystals of large size, larger than 25 mm in diameter and longer than 40 mm in length, were obtained for the alloys of composition 0<x<0.15 and 0.73<x<1 by the Czochralski technique. Single crystals of SiGe alloys (0.80<x<1) heavily doped with electrically active impurities with a concentration up to 10^<20>cm^<-3> were also successfully obtained.(2)By XAFS study … More on the local atomic structure, it is known that GeSi alloy possess random substitutional site occupancy of Si and Ge atoms but no preferential ordering across the whole composition range and that Ge-Ge and Ge-Si bond lengths maintain distinctly different lengths and vary linearly with alloy composition, to he incomplete Pauling case.(3)Oxygen impurities in the concentration of 10^<18>cm^<-3> maximum occupy preferentially a bond-center site between Si atoms to make a Si-O-Si quasi-molecule.(4)The mechanical strength of the alloys becomes temperature-insensitive at elevated temperatures and depends on the composition, being proportional to x(1-x) over the whole composition range, which may be originating in the built-in stress fields related to microscopic fluctuation of alloy composition and the dynamic interaction between dislocations.(5)Electrical and thermal conductivities and Seebeck coefficient in heavily impurity doped GeSi were evaluated for develop thermoelectric converters available at elevated temperatures. Less