Study On The Radial Resistivity Uniformity Of 4-inch P-type Low Dislocation Germanium Crystal With <100> Crystallographic Orientation For GaAs/Ge Space Solar Cell

P-type germanium single crystal as the substrate of the space solar cell epitaxial layer,the uniformity of its uniformity of resistivity has a very high demand.In germanium crystal growth by Czochralski method,Solid-liquid interface is the equal resistance surface and the same impurity concentration surface of the front crystallization.At the same time,the shape of the solid-liquid interface is directly related to the uniformity of the radial resistivity in the crystal and has a significant effect on the crystal quality.Therefore,to improve the quality of epitaxial layer is to control the crystal growth process of solid-liquid interface shape.The thermal field distribution and crystal growth process parameters of the crystal growth system affect the shape of the solid-liquid interface.In this paper,the factors influencing the shape of solid-liquid interface are studied by numerical simulation.The results of germanium crystal interface experiment and high resistivity uniformity single crystal growth experiment in TDR-Z80 furnace were consistent with the numerical simulation.The resistivity uniformity before optimization is higher than 15%.The relatively flat solid-liquid interface obtained after the optimization process greatly improves the radial resistivity uniformity and can be controlled within 5%.By establishing the numerical simulation model,the effects of process parameters such as heater,insulation layer,crucible position,crystal rotation speed,crucible rotation speed,crystal pulling rate and shoulder angle on the solid-liquid interface of the crystal growth were analyzed in the paper.According to the design,the double-heater thermal field system of the 4-inch low dislocation germanium crystal was developed.A series of numerical simulation studies are carried out on the thermal field.The numerical simulation results show that,By adopting double heater system,improving the structure of the heater,composite thermal insulation layer,suitable crucible position,optimization of process parameters can effectively control the flat solid-liquid interface of crystal growth process.Numerical simulation and experimental comparative studies show that,the numerical simulation results of solid-liquid interface are consistent with the experimental results.Optimized growth process greatly improves the radial resistivity uniformity and can be controlled within 5%.The high quality dislocation germanium crystal was developed meeting the technical requirements.