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做为衬底材料的各种掺杂和不掺杂的GaAs单晶材料中的微沉淀及微夹杂,都影响GaAs器件及集成电路的性能。我们用JEM-1000超高压电镜,采用选区电子衍射技术,研究了掺Si、掺Cr及纯度水平法生长(HB)低位错GaAs单晶中的As和C微小第二相的形态及结构。采用约化胞法、借助电子计算机计算约化胞数据表,来分析标定电子衍射花样确定结构。经电子衍射分析表明,掺Si、掺Cr及纯度水平法生(?)GaAs单晶中有二种结构类型As沉淀、一种为六方晶系As(a_0=3.76埃,c=10.55埃),另一种为正交晶系As(a_0=3.63埃,b_0=4.45埃,C_0=10.96埃),而且它们往往与α-方石英微沉淀(或微夹杂)或c微夹杂、或Cr_n As微沉淀共存(照片1)。电子衍射分析还表明,GaAs单晶中c的微夹杂是简单立方结构(a_0=5.55埃)。为了进一步验证水平法生长GaAs单晶中有c微夹杂存在,用JXA—50A扫描电子探针分析观察了,刚刚做好的电镜样品。
Micro-precipitation and micro-inclusions in various doped and undoped GaAs single-crystal materials as substrate materials all affect the performance of GaAs devices and integrated circuits. We used JEM-1000 ultra-high voltage electron microscopy and selected area electron diffraction to study the morphology and structure of As and C minor second phases in Ga-doped low-disordered GaAs single crystals doped with Si, Cr and purely level-of-purity. The reduced cell method is used to calculate the reduced cell data table by electronic computer to analyze and calibrate the electron diffraction pattern to determine the structure. The electron diffraction analysis shows that there are two kinds of As precipitates in the GaAs single crystals doped with Si, Cr and purity levels, one is hexagonal As (a_0 = 3.76 Å, c = 10.55 Å) The other is orthorhombic As (a_0 = 3.63 angstroms, b_0 = 4.45 angstroms, C_0 = 10.96 angstroms), and they are often mixed with α-cristobalite micro-precipitates (or microinclusions) or c microinclusions, or Cr_n As micro Precipitation coexists (Photo 1). Electron diffraction analysis also shows that microinclusions of c in GaAs single crystals are simple cubic structures (a_0 = 5.55 angstroms). In order to further verify the existence of c micro-inclusions in GaAs single crystal grown by horizontal method, the electron microscopy sample just observed by JXA-50A scanning electron probe was used to observe.