Carbon-containing group IV heterostructures on Si: Properties and device applications

We review some important material properties of Si_1-yC_y and Si_1-x-yGe_xC_y layers grown pseudomorphically on Si(001). This new material might overcome some of the limitations of strained Si_1-xGe_y and open new fields for device applications of heteroepitaxial Si-based systems. In addition, we demonstrated incorporating low carbon concentrations (<10²⁰ cm^-3) into the SiGe region of a heterobipolar transistor (HBT) can significantly suppress boron outdiffusion caused by later processing steps. The static characteristics demonstrate that the transistors should be suitable for circuit applications. Comparing the high-frequency performance of MBE-grown SiGe:C HBTs with identically SiGe HBTs we found an increase in f_T and f_max by a factor of more than 2 for our chosen SiGe profile. This indicates that adding carbon enabled one to use implantation steps without affecting the boron profile, that is, it offers wider latitude in process margins.