4 inch低位错密度InP单晶的VGF生长及性质研究

采用高压垂直温度梯度凝固法(VGF)生长了非掺、掺硫和掺铁的4 inch直径(100)InP单晶,获得的单晶的平均位错密度均小于5000 cm~(-2)。对4 inch InP晶片上进行多点X-射线双晶衍射测试,其(004)X-射线双晶衍射峰的半峰宽约为30弧秒且分布均匀。与液封直拉法(LEC)相比,VGF-InP单晶生长过程的温度梯度很低,导致其孪晶出现的几率显著增加。然而大量晶体生长结果表明VGF-InP晶锭上出现孪晶后,通常晶体的生长方向仍为(100)方向,这确保从生长的4 inch VGF-InP(100)晶锭上仍能获得相当数量的2~4 inch(100)晶片。由于铁在InP中的分凝系数很小,掺Fe-InP单晶VGF生长过程中容易出现组份过冷,导致多晶生长。通过控制生长温度梯度及掺铁量,可获得较高的掺铁InP单晶成晶率。对VGF-InP单晶的电学性质、位错密度及位错的分布特点、晶体完整性等进行了研究。

VGF Growth and Property of 4 inch Diameter InP Single Crystals with Low Dislocation Density

Undoped, S-doped and Fe-doped 4 inch diameter (100) InP single crystals with average dislocation etch pit density less than 5000 cm-2 have been grown by using high pressure vertical temperature gradient Freeze (VGF) method.A multiple points X-ray double crystal diffraction measurement across the 4 inch wafer indicates a full width at half maximum (FWHM) around 30 arcsec with uniform distribution of the rocking curves.Due to the low temperature gradient during the VGF growth process, the possibility of twin generation is quite high compared to that of liquid encapsulated growth process (LEC).However, the orientation of the crystal main body is still (100) direction after the twin formation on the VGF-InP crystal ingots.In this case, a large quantity of (100) single crystal wafers with diameter of 2 inch, 3 inch and 4 inch can be sliced from the ingot.Since the effective segregation coefficient is very low for Fe, polycrystal growth caused by composition super cooling of Fe-doped InP VGF is found frequently.The single crystal yield of the Fe-InP VGF growth can be increased significantly by strictly control the Fe doping quantity and the temperature gradient.Electrical property, dislocation density and its distribution, lattice perfection of the VGF-InP single crystals have been investigated.