Growth and Fundamental Properties of GeSi Bulk Crystals

锗硅（Ge_<1-x>Si_x或锗硅Si_xGe_<1-x>）合金是一种完全可混相的金刚石基固溶体，由于其提供的带隙和晶格参数工程的潜力，作为微电子和光电器件的材料引起了人们的浓厚兴趣。本研究是为了建立高质量GeSi合金单晶的生长，阐明合金化所带来的各种基本特性，以及探索这种材料广泛应用的内在特性和潜力的可能性。(1)在成分0<x<0.15和0.73<x<1的合金中，用Czochralski法获得了直径大于25 mm、长度大于40 mm的大尺寸完整单晶。还成功地获得了大量掺杂电活性杂质的SiGe合金单晶（0.80<x<1），其浓度可达10^<20>cm^<-3>。(2)通过XAFS对局部原子结构的研究，可知GeSi合金在整个组成范围内，Si和Ge原子具有随机取代位置占用，而不具有优先顺序，Ge-Ge和Ge-Si键长度随合金成分的不同而保持明显的长度差异，并呈线性变化，直至不完全Pauling情况。(3)氧杂质最大浓度为10^<18>cm^<-3>时，优先占据Si原子之间的键中心位置，形成Si- o -Si准分子。(4)合金的机械强度在高温下变得对温度不敏感，并取决于成分，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微观波动和位错之间的动态相互作用有关的内置应力场。(5)研究了重杂质掺杂GeSi热电转换器在高温下的电导率、导热率和塞贝克系数。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