The Effect Of Rotating Magnetic Field On The Growth Process Of Bridgman Method GAINSB Crystal

As a typical group Ⅲ-Ⅴ compound semiconductor material,GaInSb can be widely used in the field of detectors,lasers,optoelectronic communications,integrated circuits and satellite navigation due to its high electron mobility and narrow bandgap.However,the quality of the GaInSb crystals have not been significantly improved due to the high segregation tendency of the indium and the lack of mature preparation technology,resulting in many defects such as dislocation density in the crystal.In this paper,the rotating magnetic field was applied to the vertical Bridgman method to grow GaInSb crystal ingots.The forced convection of the rotating magnetic field was used to enhance the convection,heat transfer and mass transfer of the melt,so as to increase the uniformities of temperature distribution,the stress distribution and the solute distribution,and thus improve the solid-liquid interface shape,reduce the crystal components segregation(in particular segregation of the indium),dislocation density and other defects.The effects of rotating magnetic field frequency and intensity on the microstructure and properties of the GaInSb crystals were studied with XRD,SEM,EDS,metallographic microscope,Hall Effect testing,Raman spectroscopy,FTIR and Vickers hardness tester,and finally came to the best growth conditions and parameters.The main conclusions are as follows:(1)The rotating magnetic field(RMF)was applied to the vertical Bridgman(VB)method,and high quality Ga0.86In0.14Sb ingots Φ25 mm×100 were prepared with a homemade RMF-VB crystal growth furnace.(2)The RMF significantly improves the microstructure and properties of the GaInSb crystal ingots.With the application of RMF,the surface roughness and the crystallinity of the ingot increases.The solid-liquid interace of the ingot become flat and the segregation of indium is significantly reduced.The defects such as impurities,dislocation density and twins decrease.The carrier mobility increases,and the infrared transmittance is close to the theoretical value.(3)The effects of rotating magnetic field frequency on the microstructure and properties of the GaInSb crystal were investigated.It was found that the crystallinity of the crystal increased with the increase of the rotation frequency.When the rotation frequency was 50 Hz,the FWHM decreased to 74".The segregation of indium decreased.The radial segregation of indium could be reduced to 0.085 mol%per millimeter and the axial segregation could be reduced to 0.047 mol%per millimeter.The crystal defects decreased.When the rotation frequency was 50 Hz,the dislocation density was reduced to to 6.988×103 cm-2,and the inclusions,twins and microcracks decreased significantly.The electrical properties of the crystal were improved.The average value of the axial carrier mobility increased to 1.618×103 cm2/(V·s),and the average value of the axial resistivity decreased to 1.162×10-3 ohm·cm,meanwhile the uniformities of the axial carrier mobility and resistivity were improved.The vickers hardness of the crystal decreased.When the rotation frequency was 50 Hz,the vickers hardness of the ingot was reduced to 3.604 Gpa.(4)The effects of rotating magnetic field intensity on the microstructure and properties of the GaInSb crystal were investigated.It was found that the crystallinity of the crystal increased with the increase of the magnetic field intensity.When the magnetic field intensity was 30 mT,the FWHM of the ingot decreased to 69".The segregation of indium decreased.The radial segregation of indium was reduced to 0.086 mol%per millimeter and the axial segregation was reduced to 0.048 mol%per millimeter.The dislocation density of the crystal reduced to 6.578×1 03 cm-2.The structural defects of the crystal were significantly reduced and the crystal orientation was clearer.The crystal growth direction was(1 1 0),and the intrinsic defects were significantly reduced.The physical properties of the crystal were improved.When the magnetic field intensity was 30 mT,the carrier mobility increased to 1.738×103 cm2/(V·s),the resistivity was reduced to 1.149×10-3 ohm·cm,and the infrared transmittance increased,approaching to 36%of the theoretical value.