Fabrication and Characterization of 8 Inch Semiconducting GaAs Single Crystal Substrate
Si doped GaAs single crystal with diameter over 200 mm was prepared by vertical gradient freeze(VGF)method.The 8 inch GaAs single crystal substrate was obtained through multi-line cutting,edging,grinding,chemical mechanical polishing and wet cleaning.The crystal quality,dislocation density,electrical properties and surface quality of 8 inch GaAs substrate were characterized by X-ray diffraction,dislocation density inspection,Hall measurement,non-contact surface resistivity measurement,photoluminescence and wafer surface defect inspection.The results show that the full width of half maximum(FWHM)of substrate(400)diffraction peak is smaller than 0.009°,the average dislocation density is lower than 30 cm-2,the lowest dislocation density is 1.7 cm-2and 98.87％area are zero dislocation.Moreover,the standard deviation of surface resistivity and photoluminescence intensity are smaller than 6％and 4％,respectively.The number of the spot with light point defect(LPD)≥0.2 μm is less than 10.The results show that the 8 inch semiconducting GaAs single crystal substrate with excellent performance is developed and can be used as the high quality substrate for epitaxial growth and devices fabrication.
GaAsvertical gradient freeze8 inchsingle crystal substratedislocation density
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