高纯锗晶体内的杂质浓度与分布的研究

High pure germanium single crystal materials, of which the purity is up to 12-13N, is the world's most pure substances. This project, on the basis of key technologies of ultra-pure germanium single crystal, is going to further improve the design the new zone melting furnace and single crystal furnace in order to get the 12-13N germanium polycrystal. Furthermore, we will use the ultra-pure germanium single crystal to manufacture 0.2% energy resolution HPGe detector. The new zone melting furnace can further stabilize the narrow molten zone, and new high-purity germanium single crystal furnace is more favorable to the stability of the high-frequency heating, the quartz furnace and heater makes the thermal field distribution uniform and reduce pollution, so make sure to get low dislocation(<5000/cm2), 12-13N ultra-pure germanium single crystal. In addition that, we are also to establish the testing equipment and detection method to high pure germanium single crystal purity, dislocation and their indicators, including α particle scanning, low-temperature Hall measurements, metallographic, and liquid helium deep level Method of measurement, light thermoelectric outrageous such as the measurement of impurities. And proceed with the preparation of P-type coaxial and planar detectors, to master the key technology and process of the preparation of high purity germanium detectors, such as coating, ion diffusion, ion implantation, corrosion, sputtering, packaging, and low temperature technology.

高纯锗单晶材料，其纯度达到 12-13N，是世界上最纯的物质。本课题在本团队前期研制的基础上对超高纯锗单晶制备的关键技术和工艺进行进一步完善，设计出新的区熔炉和单晶炉以期得到纯度为 12-13N 的理想的锗多晶。同时进行应用研究，利用所制备的超高纯锗单晶制造出具有0.2%的高能量分辨率的高纯锗探测器。新的区熔炉能进一步稳定窄熔区，而新的高纯锗单晶炉更有利高频加热的稳定，石英炉体和加热器使热场分布均匀，减少污染，从而确保得到低位错（<5000/cm2）、12-13N 的超高纯锗单晶。还要建立测量超高纯鍺单晶纯度、位错等指标的检测设备和方法，包括α粒子扫描、低温霍尔测量、金相显微，以及液氦深能级、光热电离谱等测量杂质的方法。并从制备 P 型同轴型和平面型两种探测器着手，掌握高纯锗探测器制备的关键技术和工艺，如镀膜、离子扩散、离子注入、腐蚀、溅射、封装、低温等。

高纯锗探测器是目前世界上能量分辨最好的伽马射线探测器，但是目前国内还无法生产出13N的高纯锗晶体。本项目在团队前期研究的基础上，对自主设计的区熔设备与单晶炉进行了改进，并针对锗料提纯和低位错单晶的拉制进行了细致研究。区熔方面，我们通过改造线圈与电机，保证了设备能在窄熔区和低速下稳定运行。在这基础上，我们对来自同一产地的锗原料分别进了15次、20次和30次区熔。通过低温霍尔效应测量，得到了区熔次数与提纯效果的关系，发现区熔20次即可将锗的纯度提高12N以上，区熔30次能将纯度进一步提升，可以达到12.5N。单晶方面，改进了单晶炉的高频电源和加热线圈，优化了热场。通过大量实践，我们掌握了拉制低位错锗单晶的实验技术，可以将高纯锗单晶的位错密度控制在3000个/cm2以下，达到了项目预期目标。