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

Abstract

Aluminum and boron p-type low-dose implants have been characterized in 4H- and 6H-SiC for anneals from 1300 °C to 1600 °C. 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 °C anneals, usable device quality p-type layers are obtained for both SiC polytypes and implant species. For anneals at or below ∼1500 °C, 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.