Low-dose aluminum and boron implants in 4H and 6H silicon carbide

Aluminum and boron p-type low-dose implants have been characterized in 4H- and 6H-SiC for anneals from 1300 degreesC to 1600 degreesC. In contrast to previous studies of heavily doped p-type layers, here we study more lightly doped layers for use as active regions in high-voltage power devices. Activation rates of the implanted ions, depth profiles from secondary mass ion spectroscopy, and surface roughness data using atomic force microscopy are presented as a function of anneal temperature. The temperature dependence of the free hole density and hole mobility are characterized with Hall effect measurements. For 1600 degreesC anneals, usable device quality p-type layers are obtained for both SiC polytypes and implant species. For anneals at or below similar to 1500 degreesC, the implanted layers have much higher sheet resistivity due to the presence of unannealed compensating defects. These layers are not device quality. B-implanted layers have higher mobility, while activation of implanted Al is much higher and more uniform. Therefore, boron and aluminum have different advantages and disadvantages as p-type implants in SiC. (C) 2001 American Institute of Physics.