The growth of low resistivity, heavily Al-doped 4H-SiC thick epilayers by hot-wall chemical vapor deposition

Heavily Al-doped 4H-SiC thick epilayers (∼90 μm) were grown on 3-in n+ 4H-SiC wafers by using the hot-wall CVD method. On the purpose of enhancing incorporated Al-dopant concentration, the growth condition dependence of the Al incorporation behavior in the heavy doping range near Al solubility limit in 4H-SiC was investigated by varying the growth parameters, i.e., growth rate, pressure, temperature and Al-dopant source flow rate. A series of thick epilayers possessing Al-dopant concentration from 9.6×1019 to 4.7×1020 cm−3 were obtained. Among them, the epilayer with Al-dopant concentration of 3.5×1020 cm−3 demonstrates a comparably low resistivity of 16.5 mΩ cm as that of commercial n+ 4H-SiC wafer. The incorporated Al-dopant concentration dependences on surface morphology, crystalline quality and crystal structures of the heavily Al-doped thick epilayers on n+ 4H-SiC substrates were characterized and discussed.